Drilling Operations Look Inside

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8/16/2019 Drilling Operations Look Inside http://slidepdf.com/reader/full/drilling-operations-look-inside 1/33 A SigmaQuadrant Engineering Publication Cost and Risk Management Drilling Operations: Prosper Aideyan

Transcript of Drilling Operations Look Inside

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8162019 Drilling Operations Look Inside

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A SigmaQuadrantEngineering Publication

Cost and Risk

Management

Drilling Operations

Prosper Aideyan

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 233

A SigmaQuadrantEngineering Publication

Cost and Risk

Management

Drilling Operations

Prosper Aideyan

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 333

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 433

Drilling Operations

Cost and RiskManagement

8162019 Drilling Operations Look Inside

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While both the author and the publisher have used their best efforts in preparing and producing the book

they make no representations or warranties with respect to the accuracy or completeness of the contents

of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular

purpose No warranty may be created or extended by marketing or sales representatives or in print oronline sales and marketing materials The advice and strategies contained herein are the opinions of the

authors and may not be suitable for your situation You should consult with the proper professional where

appropriate Neither the publisher nor the author shall be held liable for any loss of profit or any other

commercial damages including but not limited to special incidental consequential or any other damage

This publication or any part thereof may not be copied reproduced stored in a physical or electronic

retrieval system or transmitted in any form by any means electronic mechanical photocopying

scanning recording or otherwise except as permitted under Section 107 or 108 of the 1976 United

States Copyright Act without either (1) the prior written permission of the publisher or (2) authorization

through payment of the appropriate per-copy fee to the Copyright Clearance Center 222 Rosewood Drive

Danvers Massachusetts 01923 (978) 750-8400 fax (978) 646-8600 or at wwwcopyrightcom

Drilling Operations Cost and Risk Management

Copyright copy 2015 by Sigmaquadrant LLC Houston exas All rights reserved

No part of this publication may be reproduced or transmitted in any form without the

prior written permission of the publisher

HOUSON X

SigmaQuadrantcom11306 Dawnheath Dr

Cypress X 77433

Director Dorothy Samuel

Production Editor Hubert Daniel

Senior Design Editor Balaji Srinivasan

Copy Editor Sheena Reuben

Includes bibliographical references and index

ISBN-13 978-0-990683629

10 9 8 7 6 5 4 3 2 1

1 Drilling Operations mdashEquipment and supplies 2 Oil well drillingmdashEquipment and

supplies 3 Oil well drilling 4 Gas well drilling I itle

Printed in the United States of AmericaPrinted on acid-free paper

ext design and composition by Kryon Publishing Services (P) Ltd Chennai India

wwwkryonpublishingcom

DISCLAIMER

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Drilling OperationsCost and Risk

Management

Prosper Aideyan

A SigmaQuadrant Engineering PublicationHoustonBeijingChennai

sigmaquadrantcom

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Contents

Acknowledgement ixPreface x

chapter 1

1 Risk Management Bow-ties and theldquoPPErdquo ConceptChapter Introduction 1Risk Identification 2Surface Pressure Trending 3Flow Trending 3Risk Assessment 5Responding to Risks 6

Risk Monitoring and Review 8Bow-tie Concept 9Barrier Elements PPE (People Process

and Equipment) 11Risk Management 12Compliance with Rules 12

chapter 2

15 Drilling OptimizationChapter Introduction 15Identifying Performance Improvement

Opportunities 17Drilling Optimization Work Flow 21People 21Process 23Equipment 23

Example of Drill-Off Test Procedure 27Mechanical Specific Energy 27Power Graph 33Motor and Bits Optimization 38

Torque and Drag 40

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v

chapter 3

41 Vibration

Chapter Introduction 41 Typical Causes of Drill StringBHA Failure 53Drilling Torque Reduction Possible Solutions 54

chapter 4

57 Hole CleaningChapter IntroductionBarriers 57Back Reaming 62Sweeps 66Flow Rate for Hole Cleaning 67RPM for Hole Cleaning 68Cuttings Carrying Index 70

chapter 5

75 Torque and Drag

Chapter introduction 75Drilling Torque Reduction Technique 78

chapter 6

81

Drilling Fluid Properties Maintenance

Fluid Properties Maintenance 81Barite Sag 87

chapter 7

89Wellbore Stability and LostCirculationChapter Introduction 89Wellbore Stability 89Factors affecting Wellbore Stability 93Estimation of Flow Rate Required to

Maintain Annular Velocity in Washed Hole 97

Contents

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Contents vi

chapter 8

113 Well ControlChapter IntroductionBarriers 113Riser Disconnect 117Increase in Mud Weight to Disconnect the Riser (Riser Margin) 118Estimation of Trip Margin 119Shallow GasWater 120Estimating Weight and Volume of Pump and

Dump Mud 124Using Integration Method 125Sum of Arithmetic Sequence (Arithmetic Series) 125Estimation of Discharge Flow Rate during a

Well Control Event 126

chapter 9

129

Casing Wear

Casing Wear 129

chapter 10

137Narrow Margin DrillingChapter Introduction 137Responding to Narrow Margin Drilling Risks 138Well Design 139Mud Design 139

BHA Design 140Drilling Practices 140

chapter 11

143CementingChapter IntroductionBarriers 143Centralizer Stand-Off 151Estimation of OD of Cement Stingers for

Cement Plugs 152Estimation of Under-Displacement Volume if Stinger is Used to Set a Balance Plug 156

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viiContents

chapter 12

159 Stuck Pipe Prevention and Recovery Chapter Introduction and Barriers 159Factors that Promote Differential Sticking 168Differential Sticking Potential 169Differential Stuck Pipe Recovery 171

chapter 13

177

Conductor Jetting

Chapter Introduction 177Bit Stick-Out 178Bit Space-Out 179Possibility of Reverse Jetting Angle for Stick Out Application (Upjet Nozzles) 181Comparison of Stick-Out and Space-Out 181Bit Drilled AreaHydraulically Jetted Area 182Calculation of Soak Time Required for

Conductor Casing 182Calculation of Jetted Conductor Forceto Buckling 184

Calculation of Force to Buckling in Drill Pipe 185

chapter 14

187Useful Drilling CalculationsMud Gas Separator 187Use of PWD 189Mud Compressibility 190Swab and Surge Pressures 195Estimation of Trip Margin 201Casing Slip Calculation 203Stretch Calculations 205Bit Pressure Loss 207Split FLow Between Bit and Reamer 208Kick Tolerance 227

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viii

chapter 15

233 Other Improvement Opportunities andMiscellaneous Drilling IssuesWell Trajectory Optimization 233Casing Running Improvement 240Optimizing Wellbore Monitoring 258Formation Integrity Test 261Annular Pressure Buildup 268

Glossary 283

Bibliography 305

Index 313

Contents

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Acknowledgement

he author would like to thank his family his

friends and colleagues in the course of his

career whose valuable advices and experiences helped

achieved the goal of writing this book

Special thanks to Sheena Reuben who helped us

with the copyediting and proof reading of this book Te author dedicates this book to those who work

together safely and efficiently to deliver energy to the

world

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Preface

O

ften drilling programs have documented

risks and mitigations against the identified

risks Although preventative actions against the iden-

tified risks may be expressed within the program the

emphasis is usually on the mitigation barriers against

the risks Hence it is not uncommon to see the termldquorisks and mitigationsrdquo in a drilling program Tis book

was born out of the desire to deliver the same risk man-

agement concept applied in chemical plants and refin-

eries into drilling planning and operations Barriers to

risk events should include preventative barriers and

mitigation barriers Mitigation barriers are reactive the

safety and cost of wells operations can be improved bycreating preventative barriers to reduce the chance of

the risk event occurring Mitigation barriers improve

the recovery time if a risk event should occur

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Preface xi

Tis book focuses on improving drilling operations by managing bar-

riers (both preventative and mitigation) to risk events In Chapter 1 thebasic principles of risk management are described Te chapter talks about

everything from identification of risks to creating barriers (people process

procedures and equipment) for identified risks as well as steps to help

barrier creation Chapter 2 describes the process of drilling optimization

reviewing non-productive events from offset wells or other drilling cam-

paigns categorizing non-productive time events into those that increase

ldquodrilling timerdquo and those the extend ldquoflat timerdquo and barriers to be put inplace to optimize drilling operations Chapters 3 to 13 focus on common

non-productive time events such as loss circulation well control and so on

that lead to down-time in drilling operations and barriers to the risk events

as well as monitoringcontrol barrier (eg torque and drag) Useful drilling

calculations are highlighted in Chapter 14 Chapter 15 focuses on other

continuous improvement opportunities that are not covered in Chapters

2 through 13It is my desire that this book provides useful insight into drilling

operations improvements in the area of cost and risks It is a valuable

resource for anyone involved in well planning and operations engineers

and technicians preparing risk assessments and risk workbooks engineers

involved in writing drilling procedures engineers and managers reviewing

and approving drilling programs field engineers supervisors and superin-

tendents making decisions on the fly during drilling operations and also

students wishing to pursue careers in drilling engineering and operations

Although significant effort has been made to avoid errors they are

sometimes inevitable Suggestions towards the improvement of this book

are welcome

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CHAPTER

Risk ManagementBow-ties and theldquoPPErdquo Concept

E

very activity or operation in well construc-

tion has its own associated risk(s) Te cost of

running the operation will most certainly be impacted

by the level of risk that can be taken for that partic-

ular operation ypically the running of an operation

costs less if the level of risk associated with it is highand it is higher if the level of risk is lower However

any safety incidents arising out of high-risk opera-

tions could potentially lead to catastrophic damage

which in-turn may raise the overall cost of running

the operation immensely Terefore it is important

to identify all risks associated with any operation

during well construction and to determine what levelof risk is acceptable and to what extent Risk man-

agement is the economics of finding a suitable bal-

ance between running an operation by rejecting and

1

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Drilling Operations Cost and Risk Management 10

Table 11 Comparison of preventative and mitigation barriers

Preventative Barriers Mitigation Barriers

1 Proactive Reactive

2 Reduce the likelihood of an eventoccurring

Reduce the impact of an event

3 Involve elimination preventionand control

Involve mitigation and a recovery plan

4 Usually engineering design (welltrajectory design BHA designmud design) administrativeactions (eg enforcement ofbuffer zones) andor procedural(eg ensuring pipe movement toprevent differentially stuck pipe)

Personal and environmental protectionpersonal protective equipment (PPE)and Contingency plansproceduresCan also be engineering actions (egconstruction of berms for spill contain-ment) or administrative actions (egrestricting access to only essentialpersonnel during a well control event)

Figure 13 Bow-tie for stuck pipe

Causes

High Side ForceWelbore

Trajectory

Fluid LossAdditives

ReduceOverbalance

Jars in BottomHole Assembly

(BHA)

Stuck PipeContingency Plan

Sidetrack Plan

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Stuck PipeContingency Plan

Sidetrack Plan

Stuck PipeContingency Plan

Sidetrack Plan

Jars in BHA

Jars in BHA

StuckPipe

Hazard(Drilling)

Pull Pipe intoCasing when not

Rotating and

Circulating

Stabilizers inBHADrill Pipe

Protectors onon Drill Pipe

Control DoglegSeverity

FluidsPropertiesTracking

Contact Area

ExcessiveOverbalance

Event

ConsequenceMitigation BarriersPreventative Barriers

Use SpiralDrill Collars

in Bottom HoleAssembly (BHA)

adding fluid loss additive and filter cake reduction and using spiral

drill collars stabilizers and drill pipe protectors to minimize contact

areaControl Stuck pipe event can be controlled by creating a procedure that

ensures pipe movement during repairs for surface and downhole failures

when possible and also tracking fluid properties

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Drilling Operations Cost and Risk Management 16

Drilling optimization can be broken down into the following

bull Drilling time improvement Drilling time inefficiencies are factors

that affect the rate of penetration Examples are

use of the wrong drill bit for formation drilled

poor mud motorrotary steerable system tool selection

limitation of solid handling equipment

drill string vibrationbuckling

pump limitation for hole cleaning

drill string size causing high pump pressure unavailability or inadequate procedures for hole cleaning

data transfer limitation

bull Flat time reduction Flat time inefficiencies could be as a result of

events that change drilling time to flat time or events that extend flat

time Examples of events that change drilling time to flat time are

lost circulation

motor failure MWD (measurement while drilling) failure

bit failure

drill string failure

stuck pipe

well control

wellbore instability

failure of surface and downhole equipment casing wear

Examples of events that extend flat time are

suboptimal wellbore trajectoryhole tortuosity for casing run-

ning and logging ndash longer casing runninglogging time

swabsurge during casing running

excessive breaking circulationmud conditioning

inefficiency breaking circulation while running casingpipe

leading to losses

wellbore instability while drilling loggingrunning casing

excessive time to pull out of hole with drill string due to swab

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Drilling Operations Cost and Risk Management 22

review offset risks and the result of the offset analysis should be incorporated

into the new well design Te drilling engineerteam need to involve the

stakeholders right from the beginning of the planning process Drillingengineers should involve technical specialists other teamspeers as needed

Tey should involve vendors and suppliers too in order to utilize their

specialized knowledge new technology and database of offset wells since

Figure 27 Drilling optimization process flow

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Drilling Optimization 35

Power HP E WOB ROP

N T

m

b

( ) = times times times times( )

+ times times( ) + times

minus5 054 10

377 14 6 765 10

7

minusminus times times times times

3 2 2

4

ρ Q D ROP

d e

Where

E m = Mechanical efficiency ratio

MSE = Mechanical Specific Energy (psi)

Power Graph

bull Actual Data

r h

t

f P

O R

Desired region Low MSE High ROP

Undesired region High MSE Low ROP

200

180

160

140

120

100

80

6040

20

0

MSE kpsi

0 100 200 300 400 500 600 700 800

100 HP 200 HP 400 HP 800 HP 1000 HP

Figure 216 Power curve for a deep water well

(23)

Note Most data points fall in the desired region of high ROP low MSE and thetransition zone This is because ROP is not usually an issue because the rocksrsquocompressive strengths are lower in deep water than onshore For this particularwell pump relief valve set point as well as ECD limited the ability to increase the flowrate to clean the hole better to promote better transfer of energy to the bit (lowerwellbore friction) With improved hole cleaning if ECD andor pump pressure donot limit flow rate the data points in the transition zone could have moved to thedesired zone on the plot Real time vibration data did not suggest any issues dueto vibration

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Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

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Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

8162019 Drilling Operations Look Inside

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8162019 Drilling Operations Look Inside

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A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 2: Drilling Operations Look Inside

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 233

A SigmaQuadrantEngineering Publication

Cost and Risk

Management

Drilling Operations

Prosper Aideyan

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 333

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 433

Drilling Operations

Cost and RiskManagement

8162019 Drilling Operations Look Inside

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While both the author and the publisher have used their best efforts in preparing and producing the book

they make no representations or warranties with respect to the accuracy or completeness of the contents

of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular

purpose No warranty may be created or extended by marketing or sales representatives or in print oronline sales and marketing materials The advice and strategies contained herein are the opinions of the

authors and may not be suitable for your situation You should consult with the proper professional where

appropriate Neither the publisher nor the author shall be held liable for any loss of profit or any other

commercial damages including but not limited to special incidental consequential or any other damage

This publication or any part thereof may not be copied reproduced stored in a physical or electronic

retrieval system or transmitted in any form by any means electronic mechanical photocopying

scanning recording or otherwise except as permitted under Section 107 or 108 of the 1976 United

States Copyright Act without either (1) the prior written permission of the publisher or (2) authorization

through payment of the appropriate per-copy fee to the Copyright Clearance Center 222 Rosewood Drive

Danvers Massachusetts 01923 (978) 750-8400 fax (978) 646-8600 or at wwwcopyrightcom

Drilling Operations Cost and Risk Management

Copyright copy 2015 by Sigmaquadrant LLC Houston exas All rights reserved

No part of this publication may be reproduced or transmitted in any form without the

prior written permission of the publisher

HOUSON X

SigmaQuadrantcom11306 Dawnheath Dr

Cypress X 77433

Director Dorothy Samuel

Production Editor Hubert Daniel

Senior Design Editor Balaji Srinivasan

Copy Editor Sheena Reuben

Includes bibliographical references and index

ISBN-13 978-0-990683629

10 9 8 7 6 5 4 3 2 1

1 Drilling Operations mdashEquipment and supplies 2 Oil well drillingmdashEquipment and

supplies 3 Oil well drilling 4 Gas well drilling I itle

Printed in the United States of AmericaPrinted on acid-free paper

ext design and composition by Kryon Publishing Services (P) Ltd Chennai India

wwwkryonpublishingcom

DISCLAIMER

8162019 Drilling Operations Look Inside

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Drilling OperationsCost and Risk

Management

Prosper Aideyan

A SigmaQuadrant Engineering PublicationHoustonBeijingChennai

sigmaquadrantcom

8162019 Drilling Operations Look Inside

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Contents

Acknowledgement ixPreface x

chapter 1

1 Risk Management Bow-ties and theldquoPPErdquo ConceptChapter Introduction 1Risk Identification 2Surface Pressure Trending 3Flow Trending 3Risk Assessment 5Responding to Risks 6

Risk Monitoring and Review 8Bow-tie Concept 9Barrier Elements PPE (People Process

and Equipment) 11Risk Management 12Compliance with Rules 12

chapter 2

15 Drilling OptimizationChapter Introduction 15Identifying Performance Improvement

Opportunities 17Drilling Optimization Work Flow 21People 21Process 23Equipment 23

Example of Drill-Off Test Procedure 27Mechanical Specific Energy 27Power Graph 33Motor and Bits Optimization 38

Torque and Drag 40

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v

chapter 3

41 Vibration

Chapter Introduction 41 Typical Causes of Drill StringBHA Failure 53Drilling Torque Reduction Possible Solutions 54

chapter 4

57 Hole CleaningChapter IntroductionBarriers 57Back Reaming 62Sweeps 66Flow Rate for Hole Cleaning 67RPM for Hole Cleaning 68Cuttings Carrying Index 70

chapter 5

75 Torque and Drag

Chapter introduction 75Drilling Torque Reduction Technique 78

chapter 6

81

Drilling Fluid Properties Maintenance

Fluid Properties Maintenance 81Barite Sag 87

chapter 7

89Wellbore Stability and LostCirculationChapter Introduction 89Wellbore Stability 89Factors affecting Wellbore Stability 93Estimation of Flow Rate Required to

Maintain Annular Velocity in Washed Hole 97

Contents

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Contents vi

chapter 8

113 Well ControlChapter IntroductionBarriers 113Riser Disconnect 117Increase in Mud Weight to Disconnect the Riser (Riser Margin) 118Estimation of Trip Margin 119Shallow GasWater 120Estimating Weight and Volume of Pump and

Dump Mud 124Using Integration Method 125Sum of Arithmetic Sequence (Arithmetic Series) 125Estimation of Discharge Flow Rate during a

Well Control Event 126

chapter 9

129

Casing Wear

Casing Wear 129

chapter 10

137Narrow Margin DrillingChapter Introduction 137Responding to Narrow Margin Drilling Risks 138Well Design 139Mud Design 139

BHA Design 140Drilling Practices 140

chapter 11

143CementingChapter IntroductionBarriers 143Centralizer Stand-Off 151Estimation of OD of Cement Stingers for

Cement Plugs 152Estimation of Under-Displacement Volume if Stinger is Used to Set a Balance Plug 156

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viiContents

chapter 12

159 Stuck Pipe Prevention and Recovery Chapter Introduction and Barriers 159Factors that Promote Differential Sticking 168Differential Sticking Potential 169Differential Stuck Pipe Recovery 171

chapter 13

177

Conductor Jetting

Chapter Introduction 177Bit Stick-Out 178Bit Space-Out 179Possibility of Reverse Jetting Angle for Stick Out Application (Upjet Nozzles) 181Comparison of Stick-Out and Space-Out 181Bit Drilled AreaHydraulically Jetted Area 182Calculation of Soak Time Required for

Conductor Casing 182Calculation of Jetted Conductor Forceto Buckling 184

Calculation of Force to Buckling in Drill Pipe 185

chapter 14

187Useful Drilling CalculationsMud Gas Separator 187Use of PWD 189Mud Compressibility 190Swab and Surge Pressures 195Estimation of Trip Margin 201Casing Slip Calculation 203Stretch Calculations 205Bit Pressure Loss 207Split FLow Between Bit and Reamer 208Kick Tolerance 227

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viii

chapter 15

233 Other Improvement Opportunities andMiscellaneous Drilling IssuesWell Trajectory Optimization 233Casing Running Improvement 240Optimizing Wellbore Monitoring 258Formation Integrity Test 261Annular Pressure Buildup 268

Glossary 283

Bibliography 305

Index 313

Contents

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Acknowledgement

he author would like to thank his family his

friends and colleagues in the course of his

career whose valuable advices and experiences helped

achieved the goal of writing this book

Special thanks to Sheena Reuben who helped us

with the copyediting and proof reading of this book Te author dedicates this book to those who work

together safely and efficiently to deliver energy to the

world

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Preface

O

ften drilling programs have documented

risks and mitigations against the identified

risks Although preventative actions against the iden-

tified risks may be expressed within the program the

emphasis is usually on the mitigation barriers against

the risks Hence it is not uncommon to see the termldquorisks and mitigationsrdquo in a drilling program Tis book

was born out of the desire to deliver the same risk man-

agement concept applied in chemical plants and refin-

eries into drilling planning and operations Barriers to

risk events should include preventative barriers and

mitigation barriers Mitigation barriers are reactive the

safety and cost of wells operations can be improved bycreating preventative barriers to reduce the chance of

the risk event occurring Mitigation barriers improve

the recovery time if a risk event should occur

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Preface xi

Tis book focuses on improving drilling operations by managing bar-

riers (both preventative and mitigation) to risk events In Chapter 1 thebasic principles of risk management are described Te chapter talks about

everything from identification of risks to creating barriers (people process

procedures and equipment) for identified risks as well as steps to help

barrier creation Chapter 2 describes the process of drilling optimization

reviewing non-productive events from offset wells or other drilling cam-

paigns categorizing non-productive time events into those that increase

ldquodrilling timerdquo and those the extend ldquoflat timerdquo and barriers to be put inplace to optimize drilling operations Chapters 3 to 13 focus on common

non-productive time events such as loss circulation well control and so on

that lead to down-time in drilling operations and barriers to the risk events

as well as monitoringcontrol barrier (eg torque and drag) Useful drilling

calculations are highlighted in Chapter 14 Chapter 15 focuses on other

continuous improvement opportunities that are not covered in Chapters

2 through 13It is my desire that this book provides useful insight into drilling

operations improvements in the area of cost and risks It is a valuable

resource for anyone involved in well planning and operations engineers

and technicians preparing risk assessments and risk workbooks engineers

involved in writing drilling procedures engineers and managers reviewing

and approving drilling programs field engineers supervisors and superin-

tendents making decisions on the fly during drilling operations and also

students wishing to pursue careers in drilling engineering and operations

Although significant effort has been made to avoid errors they are

sometimes inevitable Suggestions towards the improvement of this book

are welcome

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CHAPTER

Risk ManagementBow-ties and theldquoPPErdquo Concept

E

very activity or operation in well construc-

tion has its own associated risk(s) Te cost of

running the operation will most certainly be impacted

by the level of risk that can be taken for that partic-

ular operation ypically the running of an operation

costs less if the level of risk associated with it is highand it is higher if the level of risk is lower However

any safety incidents arising out of high-risk opera-

tions could potentially lead to catastrophic damage

which in-turn may raise the overall cost of running

the operation immensely Terefore it is important

to identify all risks associated with any operation

during well construction and to determine what levelof risk is acceptable and to what extent Risk man-

agement is the economics of finding a suitable bal-

ance between running an operation by rejecting and

1

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Drilling Operations Cost and Risk Management 10

Table 11 Comparison of preventative and mitigation barriers

Preventative Barriers Mitigation Barriers

1 Proactive Reactive

2 Reduce the likelihood of an eventoccurring

Reduce the impact of an event

3 Involve elimination preventionand control

Involve mitigation and a recovery plan

4 Usually engineering design (welltrajectory design BHA designmud design) administrativeactions (eg enforcement ofbuffer zones) andor procedural(eg ensuring pipe movement toprevent differentially stuck pipe)

Personal and environmental protectionpersonal protective equipment (PPE)and Contingency plansproceduresCan also be engineering actions (egconstruction of berms for spill contain-ment) or administrative actions (egrestricting access to only essentialpersonnel during a well control event)

Figure 13 Bow-tie for stuck pipe

Causes

High Side ForceWelbore

Trajectory

Fluid LossAdditives

ReduceOverbalance

Jars in BottomHole Assembly

(BHA)

Stuck PipeContingency Plan

Sidetrack Plan

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Stuck PipeContingency Plan

Sidetrack Plan

Stuck PipeContingency Plan

Sidetrack Plan

Jars in BHA

Jars in BHA

StuckPipe

Hazard(Drilling)

Pull Pipe intoCasing when not

Rotating and

Circulating

Stabilizers inBHADrill Pipe

Protectors onon Drill Pipe

Control DoglegSeverity

FluidsPropertiesTracking

Contact Area

ExcessiveOverbalance

Event

ConsequenceMitigation BarriersPreventative Barriers

Use SpiralDrill Collars

in Bottom HoleAssembly (BHA)

adding fluid loss additive and filter cake reduction and using spiral

drill collars stabilizers and drill pipe protectors to minimize contact

areaControl Stuck pipe event can be controlled by creating a procedure that

ensures pipe movement during repairs for surface and downhole failures

when possible and also tracking fluid properties

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Drilling Operations Cost and Risk Management 16

Drilling optimization can be broken down into the following

bull Drilling time improvement Drilling time inefficiencies are factors

that affect the rate of penetration Examples are

use of the wrong drill bit for formation drilled

poor mud motorrotary steerable system tool selection

limitation of solid handling equipment

drill string vibrationbuckling

pump limitation for hole cleaning

drill string size causing high pump pressure unavailability or inadequate procedures for hole cleaning

data transfer limitation

bull Flat time reduction Flat time inefficiencies could be as a result of

events that change drilling time to flat time or events that extend flat

time Examples of events that change drilling time to flat time are

lost circulation

motor failure MWD (measurement while drilling) failure

bit failure

drill string failure

stuck pipe

well control

wellbore instability

failure of surface and downhole equipment casing wear

Examples of events that extend flat time are

suboptimal wellbore trajectoryhole tortuosity for casing run-

ning and logging ndash longer casing runninglogging time

swabsurge during casing running

excessive breaking circulationmud conditioning

inefficiency breaking circulation while running casingpipe

leading to losses

wellbore instability while drilling loggingrunning casing

excessive time to pull out of hole with drill string due to swab

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Drilling Operations Cost and Risk Management 22

review offset risks and the result of the offset analysis should be incorporated

into the new well design Te drilling engineerteam need to involve the

stakeholders right from the beginning of the planning process Drillingengineers should involve technical specialists other teamspeers as needed

Tey should involve vendors and suppliers too in order to utilize their

specialized knowledge new technology and database of offset wells since

Figure 27 Drilling optimization process flow

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Drilling Optimization 35

Power HP E WOB ROP

N T

m

b

( ) = times times times times( )

+ times times( ) + times

minus5 054 10

377 14 6 765 10

7

minusminus times times times times

3 2 2

4

ρ Q D ROP

d e

Where

E m = Mechanical efficiency ratio

MSE = Mechanical Specific Energy (psi)

Power Graph

bull Actual Data

r h

t

f P

O R

Desired region Low MSE High ROP

Undesired region High MSE Low ROP

200

180

160

140

120

100

80

6040

20

0

MSE kpsi

0 100 200 300 400 500 600 700 800

100 HP 200 HP 400 HP 800 HP 1000 HP

Figure 216 Power curve for a deep water well

(23)

Note Most data points fall in the desired region of high ROP low MSE and thetransition zone This is because ROP is not usually an issue because the rocksrsquocompressive strengths are lower in deep water than onshore For this particularwell pump relief valve set point as well as ECD limited the ability to increase the flowrate to clean the hole better to promote better transfer of energy to the bit (lowerwellbore friction) With improved hole cleaning if ECD andor pump pressure donot limit flow rate the data points in the transition zone could have moved to thedesired zone on the plot Real time vibration data did not suggest any issues dueto vibration

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Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

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Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

8162019 Drilling Operations Look Inside

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

8162019 Drilling Operations Look Inside

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8162019 Drilling Operations Look Inside

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A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 3: Drilling Operations Look Inside

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8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 433

Drilling Operations

Cost and RiskManagement

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 533

While both the author and the publisher have used their best efforts in preparing and producing the book

they make no representations or warranties with respect to the accuracy or completeness of the contents

of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular

purpose No warranty may be created or extended by marketing or sales representatives or in print oronline sales and marketing materials The advice and strategies contained herein are the opinions of the

authors and may not be suitable for your situation You should consult with the proper professional where

appropriate Neither the publisher nor the author shall be held liable for any loss of profit or any other

commercial damages including but not limited to special incidental consequential or any other damage

This publication or any part thereof may not be copied reproduced stored in a physical or electronic

retrieval system or transmitted in any form by any means electronic mechanical photocopying

scanning recording or otherwise except as permitted under Section 107 or 108 of the 1976 United

States Copyright Act without either (1) the prior written permission of the publisher or (2) authorization

through payment of the appropriate per-copy fee to the Copyright Clearance Center 222 Rosewood Drive

Danvers Massachusetts 01923 (978) 750-8400 fax (978) 646-8600 or at wwwcopyrightcom

Drilling Operations Cost and Risk Management

Copyright copy 2015 by Sigmaquadrant LLC Houston exas All rights reserved

No part of this publication may be reproduced or transmitted in any form without the

prior written permission of the publisher

HOUSON X

SigmaQuadrantcom11306 Dawnheath Dr

Cypress X 77433

Director Dorothy Samuel

Production Editor Hubert Daniel

Senior Design Editor Balaji Srinivasan

Copy Editor Sheena Reuben

Includes bibliographical references and index

ISBN-13 978-0-990683629

10 9 8 7 6 5 4 3 2 1

1 Drilling Operations mdashEquipment and supplies 2 Oil well drillingmdashEquipment and

supplies 3 Oil well drilling 4 Gas well drilling I itle

Printed in the United States of AmericaPrinted on acid-free paper

ext design and composition by Kryon Publishing Services (P) Ltd Chennai India

wwwkryonpublishingcom

DISCLAIMER

8162019 Drilling Operations Look Inside

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Drilling OperationsCost and Risk

Management

Prosper Aideyan

A SigmaQuadrant Engineering PublicationHoustonBeijingChennai

sigmaquadrantcom

8162019 Drilling Operations Look Inside

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Contents

Acknowledgement ixPreface x

chapter 1

1 Risk Management Bow-ties and theldquoPPErdquo ConceptChapter Introduction 1Risk Identification 2Surface Pressure Trending 3Flow Trending 3Risk Assessment 5Responding to Risks 6

Risk Monitoring and Review 8Bow-tie Concept 9Barrier Elements PPE (People Process

and Equipment) 11Risk Management 12Compliance with Rules 12

chapter 2

15 Drilling OptimizationChapter Introduction 15Identifying Performance Improvement

Opportunities 17Drilling Optimization Work Flow 21People 21Process 23Equipment 23

Example of Drill-Off Test Procedure 27Mechanical Specific Energy 27Power Graph 33Motor and Bits Optimization 38

Torque and Drag 40

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v

chapter 3

41 Vibration

Chapter Introduction 41 Typical Causes of Drill StringBHA Failure 53Drilling Torque Reduction Possible Solutions 54

chapter 4

57 Hole CleaningChapter IntroductionBarriers 57Back Reaming 62Sweeps 66Flow Rate for Hole Cleaning 67RPM for Hole Cleaning 68Cuttings Carrying Index 70

chapter 5

75 Torque and Drag

Chapter introduction 75Drilling Torque Reduction Technique 78

chapter 6

81

Drilling Fluid Properties Maintenance

Fluid Properties Maintenance 81Barite Sag 87

chapter 7

89Wellbore Stability and LostCirculationChapter Introduction 89Wellbore Stability 89Factors affecting Wellbore Stability 93Estimation of Flow Rate Required to

Maintain Annular Velocity in Washed Hole 97

Contents

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Contents vi

chapter 8

113 Well ControlChapter IntroductionBarriers 113Riser Disconnect 117Increase in Mud Weight to Disconnect the Riser (Riser Margin) 118Estimation of Trip Margin 119Shallow GasWater 120Estimating Weight and Volume of Pump and

Dump Mud 124Using Integration Method 125Sum of Arithmetic Sequence (Arithmetic Series) 125Estimation of Discharge Flow Rate during a

Well Control Event 126

chapter 9

129

Casing Wear

Casing Wear 129

chapter 10

137Narrow Margin DrillingChapter Introduction 137Responding to Narrow Margin Drilling Risks 138Well Design 139Mud Design 139

BHA Design 140Drilling Practices 140

chapter 11

143CementingChapter IntroductionBarriers 143Centralizer Stand-Off 151Estimation of OD of Cement Stingers for

Cement Plugs 152Estimation of Under-Displacement Volume if Stinger is Used to Set a Balance Plug 156

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viiContents

chapter 12

159 Stuck Pipe Prevention and Recovery Chapter Introduction and Barriers 159Factors that Promote Differential Sticking 168Differential Sticking Potential 169Differential Stuck Pipe Recovery 171

chapter 13

177

Conductor Jetting

Chapter Introduction 177Bit Stick-Out 178Bit Space-Out 179Possibility of Reverse Jetting Angle for Stick Out Application (Upjet Nozzles) 181Comparison of Stick-Out and Space-Out 181Bit Drilled AreaHydraulically Jetted Area 182Calculation of Soak Time Required for

Conductor Casing 182Calculation of Jetted Conductor Forceto Buckling 184

Calculation of Force to Buckling in Drill Pipe 185

chapter 14

187Useful Drilling CalculationsMud Gas Separator 187Use of PWD 189Mud Compressibility 190Swab and Surge Pressures 195Estimation of Trip Margin 201Casing Slip Calculation 203Stretch Calculations 205Bit Pressure Loss 207Split FLow Between Bit and Reamer 208Kick Tolerance 227

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viii

chapter 15

233 Other Improvement Opportunities andMiscellaneous Drilling IssuesWell Trajectory Optimization 233Casing Running Improvement 240Optimizing Wellbore Monitoring 258Formation Integrity Test 261Annular Pressure Buildup 268

Glossary 283

Bibliography 305

Index 313

Contents

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Acknowledgement

he author would like to thank his family his

friends and colleagues in the course of his

career whose valuable advices and experiences helped

achieved the goal of writing this book

Special thanks to Sheena Reuben who helped us

with the copyediting and proof reading of this book Te author dedicates this book to those who work

together safely and efficiently to deliver energy to the

world

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Preface

O

ften drilling programs have documented

risks and mitigations against the identified

risks Although preventative actions against the iden-

tified risks may be expressed within the program the

emphasis is usually on the mitigation barriers against

the risks Hence it is not uncommon to see the termldquorisks and mitigationsrdquo in a drilling program Tis book

was born out of the desire to deliver the same risk man-

agement concept applied in chemical plants and refin-

eries into drilling planning and operations Barriers to

risk events should include preventative barriers and

mitigation barriers Mitigation barriers are reactive the

safety and cost of wells operations can be improved bycreating preventative barriers to reduce the chance of

the risk event occurring Mitigation barriers improve

the recovery time if a risk event should occur

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Preface xi

Tis book focuses on improving drilling operations by managing bar-

riers (both preventative and mitigation) to risk events In Chapter 1 thebasic principles of risk management are described Te chapter talks about

everything from identification of risks to creating barriers (people process

procedures and equipment) for identified risks as well as steps to help

barrier creation Chapter 2 describes the process of drilling optimization

reviewing non-productive events from offset wells or other drilling cam-

paigns categorizing non-productive time events into those that increase

ldquodrilling timerdquo and those the extend ldquoflat timerdquo and barriers to be put inplace to optimize drilling operations Chapters 3 to 13 focus on common

non-productive time events such as loss circulation well control and so on

that lead to down-time in drilling operations and barriers to the risk events

as well as monitoringcontrol barrier (eg torque and drag) Useful drilling

calculations are highlighted in Chapter 14 Chapter 15 focuses on other

continuous improvement opportunities that are not covered in Chapters

2 through 13It is my desire that this book provides useful insight into drilling

operations improvements in the area of cost and risks It is a valuable

resource for anyone involved in well planning and operations engineers

and technicians preparing risk assessments and risk workbooks engineers

involved in writing drilling procedures engineers and managers reviewing

and approving drilling programs field engineers supervisors and superin-

tendents making decisions on the fly during drilling operations and also

students wishing to pursue careers in drilling engineering and operations

Although significant effort has been made to avoid errors they are

sometimes inevitable Suggestions towards the improvement of this book

are welcome

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CHAPTER

Risk ManagementBow-ties and theldquoPPErdquo Concept

E

very activity or operation in well construc-

tion has its own associated risk(s) Te cost of

running the operation will most certainly be impacted

by the level of risk that can be taken for that partic-

ular operation ypically the running of an operation

costs less if the level of risk associated with it is highand it is higher if the level of risk is lower However

any safety incidents arising out of high-risk opera-

tions could potentially lead to catastrophic damage

which in-turn may raise the overall cost of running

the operation immensely Terefore it is important

to identify all risks associated with any operation

during well construction and to determine what levelof risk is acceptable and to what extent Risk man-

agement is the economics of finding a suitable bal-

ance between running an operation by rejecting and

1

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Drilling Operations Cost and Risk Management 10

Table 11 Comparison of preventative and mitigation barriers

Preventative Barriers Mitigation Barriers

1 Proactive Reactive

2 Reduce the likelihood of an eventoccurring

Reduce the impact of an event

3 Involve elimination preventionand control

Involve mitigation and a recovery plan

4 Usually engineering design (welltrajectory design BHA designmud design) administrativeactions (eg enforcement ofbuffer zones) andor procedural(eg ensuring pipe movement toprevent differentially stuck pipe)

Personal and environmental protectionpersonal protective equipment (PPE)and Contingency plansproceduresCan also be engineering actions (egconstruction of berms for spill contain-ment) or administrative actions (egrestricting access to only essentialpersonnel during a well control event)

Figure 13 Bow-tie for stuck pipe

Causes

High Side ForceWelbore

Trajectory

Fluid LossAdditives

ReduceOverbalance

Jars in BottomHole Assembly

(BHA)

Stuck PipeContingency Plan

Sidetrack Plan

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Stuck PipeContingency Plan

Sidetrack Plan

Stuck PipeContingency Plan

Sidetrack Plan

Jars in BHA

Jars in BHA

StuckPipe

Hazard(Drilling)

Pull Pipe intoCasing when not

Rotating and

Circulating

Stabilizers inBHADrill Pipe

Protectors onon Drill Pipe

Control DoglegSeverity

FluidsPropertiesTracking

Contact Area

ExcessiveOverbalance

Event

ConsequenceMitigation BarriersPreventative Barriers

Use SpiralDrill Collars

in Bottom HoleAssembly (BHA)

adding fluid loss additive and filter cake reduction and using spiral

drill collars stabilizers and drill pipe protectors to minimize contact

areaControl Stuck pipe event can be controlled by creating a procedure that

ensures pipe movement during repairs for surface and downhole failures

when possible and also tracking fluid properties

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Drilling Operations Cost and Risk Management 16

Drilling optimization can be broken down into the following

bull Drilling time improvement Drilling time inefficiencies are factors

that affect the rate of penetration Examples are

use of the wrong drill bit for formation drilled

poor mud motorrotary steerable system tool selection

limitation of solid handling equipment

drill string vibrationbuckling

pump limitation for hole cleaning

drill string size causing high pump pressure unavailability or inadequate procedures for hole cleaning

data transfer limitation

bull Flat time reduction Flat time inefficiencies could be as a result of

events that change drilling time to flat time or events that extend flat

time Examples of events that change drilling time to flat time are

lost circulation

motor failure MWD (measurement while drilling) failure

bit failure

drill string failure

stuck pipe

well control

wellbore instability

failure of surface and downhole equipment casing wear

Examples of events that extend flat time are

suboptimal wellbore trajectoryhole tortuosity for casing run-

ning and logging ndash longer casing runninglogging time

swabsurge during casing running

excessive breaking circulationmud conditioning

inefficiency breaking circulation while running casingpipe

leading to losses

wellbore instability while drilling loggingrunning casing

excessive time to pull out of hole with drill string due to swab

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Drilling Operations Cost and Risk Management 22

review offset risks and the result of the offset analysis should be incorporated

into the new well design Te drilling engineerteam need to involve the

stakeholders right from the beginning of the planning process Drillingengineers should involve technical specialists other teamspeers as needed

Tey should involve vendors and suppliers too in order to utilize their

specialized knowledge new technology and database of offset wells since

Figure 27 Drilling optimization process flow

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Drilling Optimization 35

Power HP E WOB ROP

N T

m

b

( ) = times times times times( )

+ times times( ) + times

minus5 054 10

377 14 6 765 10

7

minusminus times times times times

3 2 2

4

ρ Q D ROP

d e

Where

E m = Mechanical efficiency ratio

MSE = Mechanical Specific Energy (psi)

Power Graph

bull Actual Data

r h

t

f P

O R

Desired region Low MSE High ROP

Undesired region High MSE Low ROP

200

180

160

140

120

100

80

6040

20

0

MSE kpsi

0 100 200 300 400 500 600 700 800

100 HP 200 HP 400 HP 800 HP 1000 HP

Figure 216 Power curve for a deep water well

(23)

Note Most data points fall in the desired region of high ROP low MSE and thetransition zone This is because ROP is not usually an issue because the rocksrsquocompressive strengths are lower in deep water than onshore For this particularwell pump relief valve set point as well as ECD limited the ability to increase the flowrate to clean the hole better to promote better transfer of energy to the bit (lowerwellbore friction) With improved hole cleaning if ECD andor pump pressure donot limit flow rate the data points in the transition zone could have moved to thedesired zone on the plot Real time vibration data did not suggest any issues dueto vibration

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Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

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Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

8162019 Drilling Operations Look Inside

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8162019 Drilling Operations Look Inside

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A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 4: Drilling Operations Look Inside

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httpslidepdfcomreaderfulldrilling-operations-look-inside 433

Drilling Operations

Cost and RiskManagement

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 533

While both the author and the publisher have used their best efforts in preparing and producing the book

they make no representations or warranties with respect to the accuracy or completeness of the contents

of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular

purpose No warranty may be created or extended by marketing or sales representatives or in print oronline sales and marketing materials The advice and strategies contained herein are the opinions of the

authors and may not be suitable for your situation You should consult with the proper professional where

appropriate Neither the publisher nor the author shall be held liable for any loss of profit or any other

commercial damages including but not limited to special incidental consequential or any other damage

This publication or any part thereof may not be copied reproduced stored in a physical or electronic

retrieval system or transmitted in any form by any means electronic mechanical photocopying

scanning recording or otherwise except as permitted under Section 107 or 108 of the 1976 United

States Copyright Act without either (1) the prior written permission of the publisher or (2) authorization

through payment of the appropriate per-copy fee to the Copyright Clearance Center 222 Rosewood Drive

Danvers Massachusetts 01923 (978) 750-8400 fax (978) 646-8600 or at wwwcopyrightcom

Drilling Operations Cost and Risk Management

Copyright copy 2015 by Sigmaquadrant LLC Houston exas All rights reserved

No part of this publication may be reproduced or transmitted in any form without the

prior written permission of the publisher

HOUSON X

SigmaQuadrantcom11306 Dawnheath Dr

Cypress X 77433

Director Dorothy Samuel

Production Editor Hubert Daniel

Senior Design Editor Balaji Srinivasan

Copy Editor Sheena Reuben

Includes bibliographical references and index

ISBN-13 978-0-990683629

10 9 8 7 6 5 4 3 2 1

1 Drilling Operations mdashEquipment and supplies 2 Oil well drillingmdashEquipment and

supplies 3 Oil well drilling 4 Gas well drilling I itle

Printed in the United States of AmericaPrinted on acid-free paper

ext design and composition by Kryon Publishing Services (P) Ltd Chennai India

wwwkryonpublishingcom

DISCLAIMER

8162019 Drilling Operations Look Inside

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Drilling OperationsCost and Risk

Management

Prosper Aideyan

A SigmaQuadrant Engineering PublicationHoustonBeijingChennai

sigmaquadrantcom

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 733

Contents

Acknowledgement ixPreface x

chapter 1

1 Risk Management Bow-ties and theldquoPPErdquo ConceptChapter Introduction 1Risk Identification 2Surface Pressure Trending 3Flow Trending 3Risk Assessment 5Responding to Risks 6

Risk Monitoring and Review 8Bow-tie Concept 9Barrier Elements PPE (People Process

and Equipment) 11Risk Management 12Compliance with Rules 12

chapter 2

15 Drilling OptimizationChapter Introduction 15Identifying Performance Improvement

Opportunities 17Drilling Optimization Work Flow 21People 21Process 23Equipment 23

Example of Drill-Off Test Procedure 27Mechanical Specific Energy 27Power Graph 33Motor and Bits Optimization 38

Torque and Drag 40

8162019 Drilling Operations Look Inside

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v

chapter 3

41 Vibration

Chapter Introduction 41 Typical Causes of Drill StringBHA Failure 53Drilling Torque Reduction Possible Solutions 54

chapter 4

57 Hole CleaningChapter IntroductionBarriers 57Back Reaming 62Sweeps 66Flow Rate for Hole Cleaning 67RPM for Hole Cleaning 68Cuttings Carrying Index 70

chapter 5

75 Torque and Drag

Chapter introduction 75Drilling Torque Reduction Technique 78

chapter 6

81

Drilling Fluid Properties Maintenance

Fluid Properties Maintenance 81Barite Sag 87

chapter 7

89Wellbore Stability and LostCirculationChapter Introduction 89Wellbore Stability 89Factors affecting Wellbore Stability 93Estimation of Flow Rate Required to

Maintain Annular Velocity in Washed Hole 97

Contents

8162019 Drilling Operations Look Inside

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Contents vi

chapter 8

113 Well ControlChapter IntroductionBarriers 113Riser Disconnect 117Increase in Mud Weight to Disconnect the Riser (Riser Margin) 118Estimation of Trip Margin 119Shallow GasWater 120Estimating Weight and Volume of Pump and

Dump Mud 124Using Integration Method 125Sum of Arithmetic Sequence (Arithmetic Series) 125Estimation of Discharge Flow Rate during a

Well Control Event 126

chapter 9

129

Casing Wear

Casing Wear 129

chapter 10

137Narrow Margin DrillingChapter Introduction 137Responding to Narrow Margin Drilling Risks 138Well Design 139Mud Design 139

BHA Design 140Drilling Practices 140

chapter 11

143CementingChapter IntroductionBarriers 143Centralizer Stand-Off 151Estimation of OD of Cement Stingers for

Cement Plugs 152Estimation of Under-Displacement Volume if Stinger is Used to Set a Balance Plug 156

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viiContents

chapter 12

159 Stuck Pipe Prevention and Recovery Chapter Introduction and Barriers 159Factors that Promote Differential Sticking 168Differential Sticking Potential 169Differential Stuck Pipe Recovery 171

chapter 13

177

Conductor Jetting

Chapter Introduction 177Bit Stick-Out 178Bit Space-Out 179Possibility of Reverse Jetting Angle for Stick Out Application (Upjet Nozzles) 181Comparison of Stick-Out and Space-Out 181Bit Drilled AreaHydraulically Jetted Area 182Calculation of Soak Time Required for

Conductor Casing 182Calculation of Jetted Conductor Forceto Buckling 184

Calculation of Force to Buckling in Drill Pipe 185

chapter 14

187Useful Drilling CalculationsMud Gas Separator 187Use of PWD 189Mud Compressibility 190Swab and Surge Pressures 195Estimation of Trip Margin 201Casing Slip Calculation 203Stretch Calculations 205Bit Pressure Loss 207Split FLow Between Bit and Reamer 208Kick Tolerance 227

8162019 Drilling Operations Look Inside

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viii

chapter 15

233 Other Improvement Opportunities andMiscellaneous Drilling IssuesWell Trajectory Optimization 233Casing Running Improvement 240Optimizing Wellbore Monitoring 258Formation Integrity Test 261Annular Pressure Buildup 268

Glossary 283

Bibliography 305

Index 313

Contents

8162019 Drilling Operations Look Inside

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Acknowledgement

he author would like to thank his family his

friends and colleagues in the course of his

career whose valuable advices and experiences helped

achieved the goal of writing this book

Special thanks to Sheena Reuben who helped us

with the copyediting and proof reading of this book Te author dedicates this book to those who work

together safely and efficiently to deliver energy to the

world

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Preface

O

ften drilling programs have documented

risks and mitigations against the identified

risks Although preventative actions against the iden-

tified risks may be expressed within the program the

emphasis is usually on the mitigation barriers against

the risks Hence it is not uncommon to see the termldquorisks and mitigationsrdquo in a drilling program Tis book

was born out of the desire to deliver the same risk man-

agement concept applied in chemical plants and refin-

eries into drilling planning and operations Barriers to

risk events should include preventative barriers and

mitigation barriers Mitigation barriers are reactive the

safety and cost of wells operations can be improved bycreating preventative barriers to reduce the chance of

the risk event occurring Mitigation barriers improve

the recovery time if a risk event should occur

8162019 Drilling Operations Look Inside

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Preface xi

Tis book focuses on improving drilling operations by managing bar-

riers (both preventative and mitigation) to risk events In Chapter 1 thebasic principles of risk management are described Te chapter talks about

everything from identification of risks to creating barriers (people process

procedures and equipment) for identified risks as well as steps to help

barrier creation Chapter 2 describes the process of drilling optimization

reviewing non-productive events from offset wells or other drilling cam-

paigns categorizing non-productive time events into those that increase

ldquodrilling timerdquo and those the extend ldquoflat timerdquo and barriers to be put inplace to optimize drilling operations Chapters 3 to 13 focus on common

non-productive time events such as loss circulation well control and so on

that lead to down-time in drilling operations and barriers to the risk events

as well as monitoringcontrol barrier (eg torque and drag) Useful drilling

calculations are highlighted in Chapter 14 Chapter 15 focuses on other

continuous improvement opportunities that are not covered in Chapters

2 through 13It is my desire that this book provides useful insight into drilling

operations improvements in the area of cost and risks It is a valuable

resource for anyone involved in well planning and operations engineers

and technicians preparing risk assessments and risk workbooks engineers

involved in writing drilling procedures engineers and managers reviewing

and approving drilling programs field engineers supervisors and superin-

tendents making decisions on the fly during drilling operations and also

students wishing to pursue careers in drilling engineering and operations

Although significant effort has been made to avoid errors they are

sometimes inevitable Suggestions towards the improvement of this book

are welcome

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CHAPTER

Risk ManagementBow-ties and theldquoPPErdquo Concept

E

very activity or operation in well construc-

tion has its own associated risk(s) Te cost of

running the operation will most certainly be impacted

by the level of risk that can be taken for that partic-

ular operation ypically the running of an operation

costs less if the level of risk associated with it is highand it is higher if the level of risk is lower However

any safety incidents arising out of high-risk opera-

tions could potentially lead to catastrophic damage

which in-turn may raise the overall cost of running

the operation immensely Terefore it is important

to identify all risks associated with any operation

during well construction and to determine what levelof risk is acceptable and to what extent Risk man-

agement is the economics of finding a suitable bal-

ance between running an operation by rejecting and

1

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Drilling Operations Cost and Risk Management 10

Table 11 Comparison of preventative and mitigation barriers

Preventative Barriers Mitigation Barriers

1 Proactive Reactive

2 Reduce the likelihood of an eventoccurring

Reduce the impact of an event

3 Involve elimination preventionand control

Involve mitigation and a recovery plan

4 Usually engineering design (welltrajectory design BHA designmud design) administrativeactions (eg enforcement ofbuffer zones) andor procedural(eg ensuring pipe movement toprevent differentially stuck pipe)

Personal and environmental protectionpersonal protective equipment (PPE)and Contingency plansproceduresCan also be engineering actions (egconstruction of berms for spill contain-ment) or administrative actions (egrestricting access to only essentialpersonnel during a well control event)

Figure 13 Bow-tie for stuck pipe

Causes

High Side ForceWelbore

Trajectory

Fluid LossAdditives

ReduceOverbalance

Jars in BottomHole Assembly

(BHA)

Stuck PipeContingency Plan

Sidetrack Plan

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Stuck PipeContingency Plan

Sidetrack Plan

Stuck PipeContingency Plan

Sidetrack Plan

Jars in BHA

Jars in BHA

StuckPipe

Hazard(Drilling)

Pull Pipe intoCasing when not

Rotating and

Circulating

Stabilizers inBHADrill Pipe

Protectors onon Drill Pipe

Control DoglegSeverity

FluidsPropertiesTracking

Contact Area

ExcessiveOverbalance

Event

ConsequenceMitigation BarriersPreventative Barriers

Use SpiralDrill Collars

in Bottom HoleAssembly (BHA)

adding fluid loss additive and filter cake reduction and using spiral

drill collars stabilizers and drill pipe protectors to minimize contact

areaControl Stuck pipe event can be controlled by creating a procedure that

ensures pipe movement during repairs for surface and downhole failures

when possible and also tracking fluid properties

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Drilling Operations Cost and Risk Management 16

Drilling optimization can be broken down into the following

bull Drilling time improvement Drilling time inefficiencies are factors

that affect the rate of penetration Examples are

use of the wrong drill bit for formation drilled

poor mud motorrotary steerable system tool selection

limitation of solid handling equipment

drill string vibrationbuckling

pump limitation for hole cleaning

drill string size causing high pump pressure unavailability or inadequate procedures for hole cleaning

data transfer limitation

bull Flat time reduction Flat time inefficiencies could be as a result of

events that change drilling time to flat time or events that extend flat

time Examples of events that change drilling time to flat time are

lost circulation

motor failure MWD (measurement while drilling) failure

bit failure

drill string failure

stuck pipe

well control

wellbore instability

failure of surface and downhole equipment casing wear

Examples of events that extend flat time are

suboptimal wellbore trajectoryhole tortuosity for casing run-

ning and logging ndash longer casing runninglogging time

swabsurge during casing running

excessive breaking circulationmud conditioning

inefficiency breaking circulation while running casingpipe

leading to losses

wellbore instability while drilling loggingrunning casing

excessive time to pull out of hole with drill string due to swab

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Drilling Operations Cost and Risk Management 22

review offset risks and the result of the offset analysis should be incorporated

into the new well design Te drilling engineerteam need to involve the

stakeholders right from the beginning of the planning process Drillingengineers should involve technical specialists other teamspeers as needed

Tey should involve vendors and suppliers too in order to utilize their

specialized knowledge new technology and database of offset wells since

Figure 27 Drilling optimization process flow

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Drilling Optimization 35

Power HP E WOB ROP

N T

m

b

( ) = times times times times( )

+ times times( ) + times

minus5 054 10

377 14 6 765 10

7

minusminus times times times times

3 2 2

4

ρ Q D ROP

d e

Where

E m = Mechanical efficiency ratio

MSE = Mechanical Specific Energy (psi)

Power Graph

bull Actual Data

r h

t

f P

O R

Desired region Low MSE High ROP

Undesired region High MSE Low ROP

200

180

160

140

120

100

80

6040

20

0

MSE kpsi

0 100 200 300 400 500 600 700 800

100 HP 200 HP 400 HP 800 HP 1000 HP

Figure 216 Power curve for a deep water well

(23)

Note Most data points fall in the desired region of high ROP low MSE and thetransition zone This is because ROP is not usually an issue because the rocksrsquocompressive strengths are lower in deep water than onshore For this particularwell pump relief valve set point as well as ECD limited the ability to increase the flowrate to clean the hole better to promote better transfer of energy to the bit (lowerwellbore friction) With improved hole cleaning if ECD andor pump pressure donot limit flow rate the data points in the transition zone could have moved to thedesired zone on the plot Real time vibration data did not suggest any issues dueto vibration

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Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

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Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

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8162019 Drilling Operations Look Inside

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A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 5: Drilling Operations Look Inside

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 533

While both the author and the publisher have used their best efforts in preparing and producing the book

they make no representations or warranties with respect to the accuracy or completeness of the contents

of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular

purpose No warranty may be created or extended by marketing or sales representatives or in print oronline sales and marketing materials The advice and strategies contained herein are the opinions of the

authors and may not be suitable for your situation You should consult with the proper professional where

appropriate Neither the publisher nor the author shall be held liable for any loss of profit or any other

commercial damages including but not limited to special incidental consequential or any other damage

This publication or any part thereof may not be copied reproduced stored in a physical or electronic

retrieval system or transmitted in any form by any means electronic mechanical photocopying

scanning recording or otherwise except as permitted under Section 107 or 108 of the 1976 United

States Copyright Act without either (1) the prior written permission of the publisher or (2) authorization

through payment of the appropriate per-copy fee to the Copyright Clearance Center 222 Rosewood Drive

Danvers Massachusetts 01923 (978) 750-8400 fax (978) 646-8600 or at wwwcopyrightcom

Drilling Operations Cost and Risk Management

Copyright copy 2015 by Sigmaquadrant LLC Houston exas All rights reserved

No part of this publication may be reproduced or transmitted in any form without the

prior written permission of the publisher

HOUSON X

SigmaQuadrantcom11306 Dawnheath Dr

Cypress X 77433

Director Dorothy Samuel

Production Editor Hubert Daniel

Senior Design Editor Balaji Srinivasan

Copy Editor Sheena Reuben

Includes bibliographical references and index

ISBN-13 978-0-990683629

10 9 8 7 6 5 4 3 2 1

1 Drilling Operations mdashEquipment and supplies 2 Oil well drillingmdashEquipment and

supplies 3 Oil well drilling 4 Gas well drilling I itle

Printed in the United States of AmericaPrinted on acid-free paper

ext design and composition by Kryon Publishing Services (P) Ltd Chennai India

wwwkryonpublishingcom

DISCLAIMER

8162019 Drilling Operations Look Inside

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Drilling OperationsCost and Risk

Management

Prosper Aideyan

A SigmaQuadrant Engineering PublicationHoustonBeijingChennai

sigmaquadrantcom

8162019 Drilling Operations Look Inside

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Contents

Acknowledgement ixPreface x

chapter 1

1 Risk Management Bow-ties and theldquoPPErdquo ConceptChapter Introduction 1Risk Identification 2Surface Pressure Trending 3Flow Trending 3Risk Assessment 5Responding to Risks 6

Risk Monitoring and Review 8Bow-tie Concept 9Barrier Elements PPE (People Process

and Equipment) 11Risk Management 12Compliance with Rules 12

chapter 2

15 Drilling OptimizationChapter Introduction 15Identifying Performance Improvement

Opportunities 17Drilling Optimization Work Flow 21People 21Process 23Equipment 23

Example of Drill-Off Test Procedure 27Mechanical Specific Energy 27Power Graph 33Motor and Bits Optimization 38

Torque and Drag 40

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v

chapter 3

41 Vibration

Chapter Introduction 41 Typical Causes of Drill StringBHA Failure 53Drilling Torque Reduction Possible Solutions 54

chapter 4

57 Hole CleaningChapter IntroductionBarriers 57Back Reaming 62Sweeps 66Flow Rate for Hole Cleaning 67RPM for Hole Cleaning 68Cuttings Carrying Index 70

chapter 5

75 Torque and Drag

Chapter introduction 75Drilling Torque Reduction Technique 78

chapter 6

81

Drilling Fluid Properties Maintenance

Fluid Properties Maintenance 81Barite Sag 87

chapter 7

89Wellbore Stability and LostCirculationChapter Introduction 89Wellbore Stability 89Factors affecting Wellbore Stability 93Estimation of Flow Rate Required to

Maintain Annular Velocity in Washed Hole 97

Contents

8162019 Drilling Operations Look Inside

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Contents vi

chapter 8

113 Well ControlChapter IntroductionBarriers 113Riser Disconnect 117Increase in Mud Weight to Disconnect the Riser (Riser Margin) 118Estimation of Trip Margin 119Shallow GasWater 120Estimating Weight and Volume of Pump and

Dump Mud 124Using Integration Method 125Sum of Arithmetic Sequence (Arithmetic Series) 125Estimation of Discharge Flow Rate during a

Well Control Event 126

chapter 9

129

Casing Wear

Casing Wear 129

chapter 10

137Narrow Margin DrillingChapter Introduction 137Responding to Narrow Margin Drilling Risks 138Well Design 139Mud Design 139

BHA Design 140Drilling Practices 140

chapter 11

143CementingChapter IntroductionBarriers 143Centralizer Stand-Off 151Estimation of OD of Cement Stingers for

Cement Plugs 152Estimation of Under-Displacement Volume if Stinger is Used to Set a Balance Plug 156

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viiContents

chapter 12

159 Stuck Pipe Prevention and Recovery Chapter Introduction and Barriers 159Factors that Promote Differential Sticking 168Differential Sticking Potential 169Differential Stuck Pipe Recovery 171

chapter 13

177

Conductor Jetting

Chapter Introduction 177Bit Stick-Out 178Bit Space-Out 179Possibility of Reverse Jetting Angle for Stick Out Application (Upjet Nozzles) 181Comparison of Stick-Out and Space-Out 181Bit Drilled AreaHydraulically Jetted Area 182Calculation of Soak Time Required for

Conductor Casing 182Calculation of Jetted Conductor Forceto Buckling 184

Calculation of Force to Buckling in Drill Pipe 185

chapter 14

187Useful Drilling CalculationsMud Gas Separator 187Use of PWD 189Mud Compressibility 190Swab and Surge Pressures 195Estimation of Trip Margin 201Casing Slip Calculation 203Stretch Calculations 205Bit Pressure Loss 207Split FLow Between Bit and Reamer 208Kick Tolerance 227

8162019 Drilling Operations Look Inside

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viii

chapter 15

233 Other Improvement Opportunities andMiscellaneous Drilling IssuesWell Trajectory Optimization 233Casing Running Improvement 240Optimizing Wellbore Monitoring 258Formation Integrity Test 261Annular Pressure Buildup 268

Glossary 283

Bibliography 305

Index 313

Contents

8162019 Drilling Operations Look Inside

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Acknowledgement

he author would like to thank his family his

friends and colleagues in the course of his

career whose valuable advices and experiences helped

achieved the goal of writing this book

Special thanks to Sheena Reuben who helped us

with the copyediting and proof reading of this book Te author dedicates this book to those who work

together safely and efficiently to deliver energy to the

world

8162019 Drilling Operations Look Inside

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Preface

O

ften drilling programs have documented

risks and mitigations against the identified

risks Although preventative actions against the iden-

tified risks may be expressed within the program the

emphasis is usually on the mitigation barriers against

the risks Hence it is not uncommon to see the termldquorisks and mitigationsrdquo in a drilling program Tis book

was born out of the desire to deliver the same risk man-

agement concept applied in chemical plants and refin-

eries into drilling planning and operations Barriers to

risk events should include preventative barriers and

mitigation barriers Mitigation barriers are reactive the

safety and cost of wells operations can be improved bycreating preventative barriers to reduce the chance of

the risk event occurring Mitigation barriers improve

the recovery time if a risk event should occur

8162019 Drilling Operations Look Inside

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Preface xi

Tis book focuses on improving drilling operations by managing bar-

riers (both preventative and mitigation) to risk events In Chapter 1 thebasic principles of risk management are described Te chapter talks about

everything from identification of risks to creating barriers (people process

procedures and equipment) for identified risks as well as steps to help

barrier creation Chapter 2 describes the process of drilling optimization

reviewing non-productive events from offset wells or other drilling cam-

paigns categorizing non-productive time events into those that increase

ldquodrilling timerdquo and those the extend ldquoflat timerdquo and barriers to be put inplace to optimize drilling operations Chapters 3 to 13 focus on common

non-productive time events such as loss circulation well control and so on

that lead to down-time in drilling operations and barriers to the risk events

as well as monitoringcontrol barrier (eg torque and drag) Useful drilling

calculations are highlighted in Chapter 14 Chapter 15 focuses on other

continuous improvement opportunities that are not covered in Chapters

2 through 13It is my desire that this book provides useful insight into drilling

operations improvements in the area of cost and risks It is a valuable

resource for anyone involved in well planning and operations engineers

and technicians preparing risk assessments and risk workbooks engineers

involved in writing drilling procedures engineers and managers reviewing

and approving drilling programs field engineers supervisors and superin-

tendents making decisions on the fly during drilling operations and also

students wishing to pursue careers in drilling engineering and operations

Although significant effort has been made to avoid errors they are

sometimes inevitable Suggestions towards the improvement of this book

are welcome

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CHAPTER

Risk ManagementBow-ties and theldquoPPErdquo Concept

E

very activity or operation in well construc-

tion has its own associated risk(s) Te cost of

running the operation will most certainly be impacted

by the level of risk that can be taken for that partic-

ular operation ypically the running of an operation

costs less if the level of risk associated with it is highand it is higher if the level of risk is lower However

any safety incidents arising out of high-risk opera-

tions could potentially lead to catastrophic damage

which in-turn may raise the overall cost of running

the operation immensely Terefore it is important

to identify all risks associated with any operation

during well construction and to determine what levelof risk is acceptable and to what extent Risk man-

agement is the economics of finding a suitable bal-

ance between running an operation by rejecting and

1

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 10

Table 11 Comparison of preventative and mitigation barriers

Preventative Barriers Mitigation Barriers

1 Proactive Reactive

2 Reduce the likelihood of an eventoccurring

Reduce the impact of an event

3 Involve elimination preventionand control

Involve mitigation and a recovery plan

4 Usually engineering design (welltrajectory design BHA designmud design) administrativeactions (eg enforcement ofbuffer zones) andor procedural(eg ensuring pipe movement toprevent differentially stuck pipe)

Personal and environmental protectionpersonal protective equipment (PPE)and Contingency plansproceduresCan also be engineering actions (egconstruction of berms for spill contain-ment) or administrative actions (egrestricting access to only essentialpersonnel during a well control event)

Figure 13 Bow-tie for stuck pipe

Causes

High Side ForceWelbore

Trajectory

Fluid LossAdditives

ReduceOverbalance

Jars in BottomHole Assembly

(BHA)

Stuck PipeContingency Plan

Sidetrack Plan

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Stuck PipeContingency Plan

Sidetrack Plan

Stuck PipeContingency Plan

Sidetrack Plan

Jars in BHA

Jars in BHA

StuckPipe

Hazard(Drilling)

Pull Pipe intoCasing when not

Rotating and

Circulating

Stabilizers inBHADrill Pipe

Protectors onon Drill Pipe

Control DoglegSeverity

FluidsPropertiesTracking

Contact Area

ExcessiveOverbalance

Event

ConsequenceMitigation BarriersPreventative Barriers

Use SpiralDrill Collars

in Bottom HoleAssembly (BHA)

adding fluid loss additive and filter cake reduction and using spiral

drill collars stabilizers and drill pipe protectors to minimize contact

areaControl Stuck pipe event can be controlled by creating a procedure that

ensures pipe movement during repairs for surface and downhole failures

when possible and also tracking fluid properties

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Drilling Operations Cost and Risk Management 16

Drilling optimization can be broken down into the following

bull Drilling time improvement Drilling time inefficiencies are factors

that affect the rate of penetration Examples are

use of the wrong drill bit for formation drilled

poor mud motorrotary steerable system tool selection

limitation of solid handling equipment

drill string vibrationbuckling

pump limitation for hole cleaning

drill string size causing high pump pressure unavailability or inadequate procedures for hole cleaning

data transfer limitation

bull Flat time reduction Flat time inefficiencies could be as a result of

events that change drilling time to flat time or events that extend flat

time Examples of events that change drilling time to flat time are

lost circulation

motor failure MWD (measurement while drilling) failure

bit failure

drill string failure

stuck pipe

well control

wellbore instability

failure of surface and downhole equipment casing wear

Examples of events that extend flat time are

suboptimal wellbore trajectoryhole tortuosity for casing run-

ning and logging ndash longer casing runninglogging time

swabsurge during casing running

excessive breaking circulationmud conditioning

inefficiency breaking circulation while running casingpipe

leading to losses

wellbore instability while drilling loggingrunning casing

excessive time to pull out of hole with drill string due to swab

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Drilling Operations Cost and Risk Management 22

review offset risks and the result of the offset analysis should be incorporated

into the new well design Te drilling engineerteam need to involve the

stakeholders right from the beginning of the planning process Drillingengineers should involve technical specialists other teamspeers as needed

Tey should involve vendors and suppliers too in order to utilize their

specialized knowledge new technology and database of offset wells since

Figure 27 Drilling optimization process flow

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Drilling Optimization 35

Power HP E WOB ROP

N T

m

b

( ) = times times times times( )

+ times times( ) + times

minus5 054 10

377 14 6 765 10

7

minusminus times times times times

3 2 2

4

ρ Q D ROP

d e

Where

E m = Mechanical efficiency ratio

MSE = Mechanical Specific Energy (psi)

Power Graph

bull Actual Data

r h

t

f P

O R

Desired region Low MSE High ROP

Undesired region High MSE Low ROP

200

180

160

140

120

100

80

6040

20

0

MSE kpsi

0 100 200 300 400 500 600 700 800

100 HP 200 HP 400 HP 800 HP 1000 HP

Figure 216 Power curve for a deep water well

(23)

Note Most data points fall in the desired region of high ROP low MSE and thetransition zone This is because ROP is not usually an issue because the rocksrsquocompressive strengths are lower in deep water than onshore For this particularwell pump relief valve set point as well as ECD limited the ability to increase the flowrate to clean the hole better to promote better transfer of energy to the bit (lowerwellbore friction) With improved hole cleaning if ECD andor pump pressure donot limit flow rate the data points in the transition zone could have moved to thedesired zone on the plot Real time vibration data did not suggest any issues dueto vibration

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Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

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Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

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8162019 Drilling Operations Look Inside

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A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 6: Drilling Operations Look Inside

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Drilling OperationsCost and Risk

Management

Prosper Aideyan

A SigmaQuadrant Engineering PublicationHoustonBeijingChennai

sigmaquadrantcom

8162019 Drilling Operations Look Inside

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Contents

Acknowledgement ixPreface x

chapter 1

1 Risk Management Bow-ties and theldquoPPErdquo ConceptChapter Introduction 1Risk Identification 2Surface Pressure Trending 3Flow Trending 3Risk Assessment 5Responding to Risks 6

Risk Monitoring and Review 8Bow-tie Concept 9Barrier Elements PPE (People Process

and Equipment) 11Risk Management 12Compliance with Rules 12

chapter 2

15 Drilling OptimizationChapter Introduction 15Identifying Performance Improvement

Opportunities 17Drilling Optimization Work Flow 21People 21Process 23Equipment 23

Example of Drill-Off Test Procedure 27Mechanical Specific Energy 27Power Graph 33Motor and Bits Optimization 38

Torque and Drag 40

8162019 Drilling Operations Look Inside

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v

chapter 3

41 Vibration

Chapter Introduction 41 Typical Causes of Drill StringBHA Failure 53Drilling Torque Reduction Possible Solutions 54

chapter 4

57 Hole CleaningChapter IntroductionBarriers 57Back Reaming 62Sweeps 66Flow Rate for Hole Cleaning 67RPM for Hole Cleaning 68Cuttings Carrying Index 70

chapter 5

75 Torque and Drag

Chapter introduction 75Drilling Torque Reduction Technique 78

chapter 6

81

Drilling Fluid Properties Maintenance

Fluid Properties Maintenance 81Barite Sag 87

chapter 7

89Wellbore Stability and LostCirculationChapter Introduction 89Wellbore Stability 89Factors affecting Wellbore Stability 93Estimation of Flow Rate Required to

Maintain Annular Velocity in Washed Hole 97

Contents

8162019 Drilling Operations Look Inside

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Contents vi

chapter 8

113 Well ControlChapter IntroductionBarriers 113Riser Disconnect 117Increase in Mud Weight to Disconnect the Riser (Riser Margin) 118Estimation of Trip Margin 119Shallow GasWater 120Estimating Weight and Volume of Pump and

Dump Mud 124Using Integration Method 125Sum of Arithmetic Sequence (Arithmetic Series) 125Estimation of Discharge Flow Rate during a

Well Control Event 126

chapter 9

129

Casing Wear

Casing Wear 129

chapter 10

137Narrow Margin DrillingChapter Introduction 137Responding to Narrow Margin Drilling Risks 138Well Design 139Mud Design 139

BHA Design 140Drilling Practices 140

chapter 11

143CementingChapter IntroductionBarriers 143Centralizer Stand-Off 151Estimation of OD of Cement Stingers for

Cement Plugs 152Estimation of Under-Displacement Volume if Stinger is Used to Set a Balance Plug 156

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viiContents

chapter 12

159 Stuck Pipe Prevention and Recovery Chapter Introduction and Barriers 159Factors that Promote Differential Sticking 168Differential Sticking Potential 169Differential Stuck Pipe Recovery 171

chapter 13

177

Conductor Jetting

Chapter Introduction 177Bit Stick-Out 178Bit Space-Out 179Possibility of Reverse Jetting Angle for Stick Out Application (Upjet Nozzles) 181Comparison of Stick-Out and Space-Out 181Bit Drilled AreaHydraulically Jetted Area 182Calculation of Soak Time Required for

Conductor Casing 182Calculation of Jetted Conductor Forceto Buckling 184

Calculation of Force to Buckling in Drill Pipe 185

chapter 14

187Useful Drilling CalculationsMud Gas Separator 187Use of PWD 189Mud Compressibility 190Swab and Surge Pressures 195Estimation of Trip Margin 201Casing Slip Calculation 203Stretch Calculations 205Bit Pressure Loss 207Split FLow Between Bit and Reamer 208Kick Tolerance 227

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viii

chapter 15

233 Other Improvement Opportunities andMiscellaneous Drilling IssuesWell Trajectory Optimization 233Casing Running Improvement 240Optimizing Wellbore Monitoring 258Formation Integrity Test 261Annular Pressure Buildup 268

Glossary 283

Bibliography 305

Index 313

Contents

8162019 Drilling Operations Look Inside

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Acknowledgement

he author would like to thank his family his

friends and colleagues in the course of his

career whose valuable advices and experiences helped

achieved the goal of writing this book

Special thanks to Sheena Reuben who helped us

with the copyediting and proof reading of this book Te author dedicates this book to those who work

together safely and efficiently to deliver energy to the

world

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Preface

O

ften drilling programs have documented

risks and mitigations against the identified

risks Although preventative actions against the iden-

tified risks may be expressed within the program the

emphasis is usually on the mitigation barriers against

the risks Hence it is not uncommon to see the termldquorisks and mitigationsrdquo in a drilling program Tis book

was born out of the desire to deliver the same risk man-

agement concept applied in chemical plants and refin-

eries into drilling planning and operations Barriers to

risk events should include preventative barriers and

mitigation barriers Mitigation barriers are reactive the

safety and cost of wells operations can be improved bycreating preventative barriers to reduce the chance of

the risk event occurring Mitigation barriers improve

the recovery time if a risk event should occur

8162019 Drilling Operations Look Inside

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Preface xi

Tis book focuses on improving drilling operations by managing bar-

riers (both preventative and mitigation) to risk events In Chapter 1 thebasic principles of risk management are described Te chapter talks about

everything from identification of risks to creating barriers (people process

procedures and equipment) for identified risks as well as steps to help

barrier creation Chapter 2 describes the process of drilling optimization

reviewing non-productive events from offset wells or other drilling cam-

paigns categorizing non-productive time events into those that increase

ldquodrilling timerdquo and those the extend ldquoflat timerdquo and barriers to be put inplace to optimize drilling operations Chapters 3 to 13 focus on common

non-productive time events such as loss circulation well control and so on

that lead to down-time in drilling operations and barriers to the risk events

as well as monitoringcontrol barrier (eg torque and drag) Useful drilling

calculations are highlighted in Chapter 14 Chapter 15 focuses on other

continuous improvement opportunities that are not covered in Chapters

2 through 13It is my desire that this book provides useful insight into drilling

operations improvements in the area of cost and risks It is a valuable

resource for anyone involved in well planning and operations engineers

and technicians preparing risk assessments and risk workbooks engineers

involved in writing drilling procedures engineers and managers reviewing

and approving drilling programs field engineers supervisors and superin-

tendents making decisions on the fly during drilling operations and also

students wishing to pursue careers in drilling engineering and operations

Although significant effort has been made to avoid errors they are

sometimes inevitable Suggestions towards the improvement of this book

are welcome

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CHAPTER

Risk ManagementBow-ties and theldquoPPErdquo Concept

E

very activity or operation in well construc-

tion has its own associated risk(s) Te cost of

running the operation will most certainly be impacted

by the level of risk that can be taken for that partic-

ular operation ypically the running of an operation

costs less if the level of risk associated with it is highand it is higher if the level of risk is lower However

any safety incidents arising out of high-risk opera-

tions could potentially lead to catastrophic damage

which in-turn may raise the overall cost of running

the operation immensely Terefore it is important

to identify all risks associated with any operation

during well construction and to determine what levelof risk is acceptable and to what extent Risk man-

agement is the economics of finding a suitable bal-

ance between running an operation by rejecting and

1

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Drilling Operations Cost and Risk Management 10

Table 11 Comparison of preventative and mitigation barriers

Preventative Barriers Mitigation Barriers

1 Proactive Reactive

2 Reduce the likelihood of an eventoccurring

Reduce the impact of an event

3 Involve elimination preventionand control

Involve mitigation and a recovery plan

4 Usually engineering design (welltrajectory design BHA designmud design) administrativeactions (eg enforcement ofbuffer zones) andor procedural(eg ensuring pipe movement toprevent differentially stuck pipe)

Personal and environmental protectionpersonal protective equipment (PPE)and Contingency plansproceduresCan also be engineering actions (egconstruction of berms for spill contain-ment) or administrative actions (egrestricting access to only essentialpersonnel during a well control event)

Figure 13 Bow-tie for stuck pipe

Causes

High Side ForceWelbore

Trajectory

Fluid LossAdditives

ReduceOverbalance

Jars in BottomHole Assembly

(BHA)

Stuck PipeContingency Plan

Sidetrack Plan

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Stuck PipeContingency Plan

Sidetrack Plan

Stuck PipeContingency Plan

Sidetrack Plan

Jars in BHA

Jars in BHA

StuckPipe

Hazard(Drilling)

Pull Pipe intoCasing when not

Rotating and

Circulating

Stabilizers inBHADrill Pipe

Protectors onon Drill Pipe

Control DoglegSeverity

FluidsPropertiesTracking

Contact Area

ExcessiveOverbalance

Event

ConsequenceMitigation BarriersPreventative Barriers

Use SpiralDrill Collars

in Bottom HoleAssembly (BHA)

adding fluid loss additive and filter cake reduction and using spiral

drill collars stabilizers and drill pipe protectors to minimize contact

areaControl Stuck pipe event can be controlled by creating a procedure that

ensures pipe movement during repairs for surface and downhole failures

when possible and also tracking fluid properties

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Drilling Operations Cost and Risk Management 16

Drilling optimization can be broken down into the following

bull Drilling time improvement Drilling time inefficiencies are factors

that affect the rate of penetration Examples are

use of the wrong drill bit for formation drilled

poor mud motorrotary steerable system tool selection

limitation of solid handling equipment

drill string vibrationbuckling

pump limitation for hole cleaning

drill string size causing high pump pressure unavailability or inadequate procedures for hole cleaning

data transfer limitation

bull Flat time reduction Flat time inefficiencies could be as a result of

events that change drilling time to flat time or events that extend flat

time Examples of events that change drilling time to flat time are

lost circulation

motor failure MWD (measurement while drilling) failure

bit failure

drill string failure

stuck pipe

well control

wellbore instability

failure of surface and downhole equipment casing wear

Examples of events that extend flat time are

suboptimal wellbore trajectoryhole tortuosity for casing run-

ning and logging ndash longer casing runninglogging time

swabsurge during casing running

excessive breaking circulationmud conditioning

inefficiency breaking circulation while running casingpipe

leading to losses

wellbore instability while drilling loggingrunning casing

excessive time to pull out of hole with drill string due to swab

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Drilling Operations Cost and Risk Management 22

review offset risks and the result of the offset analysis should be incorporated

into the new well design Te drilling engineerteam need to involve the

stakeholders right from the beginning of the planning process Drillingengineers should involve technical specialists other teamspeers as needed

Tey should involve vendors and suppliers too in order to utilize their

specialized knowledge new technology and database of offset wells since

Figure 27 Drilling optimization process flow

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Drilling Optimization 35

Power HP E WOB ROP

N T

m

b

( ) = times times times times( )

+ times times( ) + times

minus5 054 10

377 14 6 765 10

7

minusminus times times times times

3 2 2

4

ρ Q D ROP

d e

Where

E m = Mechanical efficiency ratio

MSE = Mechanical Specific Energy (psi)

Power Graph

bull Actual Data

r h

t

f P

O R

Desired region Low MSE High ROP

Undesired region High MSE Low ROP

200

180

160

140

120

100

80

6040

20

0

MSE kpsi

0 100 200 300 400 500 600 700 800

100 HP 200 HP 400 HP 800 HP 1000 HP

Figure 216 Power curve for a deep water well

(23)

Note Most data points fall in the desired region of high ROP low MSE and thetransition zone This is because ROP is not usually an issue because the rocksrsquocompressive strengths are lower in deep water than onshore For this particularwell pump relief valve set point as well as ECD limited the ability to increase the flowrate to clean the hole better to promote better transfer of energy to the bit (lowerwellbore friction) With improved hole cleaning if ECD andor pump pressure donot limit flow rate the data points in the transition zone could have moved to thedesired zone on the plot Real time vibration data did not suggest any issues dueto vibration

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Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

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Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

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A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 7: Drilling Operations Look Inside

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Contents

Acknowledgement ixPreface x

chapter 1

1 Risk Management Bow-ties and theldquoPPErdquo ConceptChapter Introduction 1Risk Identification 2Surface Pressure Trending 3Flow Trending 3Risk Assessment 5Responding to Risks 6

Risk Monitoring and Review 8Bow-tie Concept 9Barrier Elements PPE (People Process

and Equipment) 11Risk Management 12Compliance with Rules 12

chapter 2

15 Drilling OptimizationChapter Introduction 15Identifying Performance Improvement

Opportunities 17Drilling Optimization Work Flow 21People 21Process 23Equipment 23

Example of Drill-Off Test Procedure 27Mechanical Specific Energy 27Power Graph 33Motor and Bits Optimization 38

Torque and Drag 40

8162019 Drilling Operations Look Inside

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v

chapter 3

41 Vibration

Chapter Introduction 41 Typical Causes of Drill StringBHA Failure 53Drilling Torque Reduction Possible Solutions 54

chapter 4

57 Hole CleaningChapter IntroductionBarriers 57Back Reaming 62Sweeps 66Flow Rate for Hole Cleaning 67RPM for Hole Cleaning 68Cuttings Carrying Index 70

chapter 5

75 Torque and Drag

Chapter introduction 75Drilling Torque Reduction Technique 78

chapter 6

81

Drilling Fluid Properties Maintenance

Fluid Properties Maintenance 81Barite Sag 87

chapter 7

89Wellbore Stability and LostCirculationChapter Introduction 89Wellbore Stability 89Factors affecting Wellbore Stability 93Estimation of Flow Rate Required to

Maintain Annular Velocity in Washed Hole 97

Contents

8162019 Drilling Operations Look Inside

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Contents vi

chapter 8

113 Well ControlChapter IntroductionBarriers 113Riser Disconnect 117Increase in Mud Weight to Disconnect the Riser (Riser Margin) 118Estimation of Trip Margin 119Shallow GasWater 120Estimating Weight and Volume of Pump and

Dump Mud 124Using Integration Method 125Sum of Arithmetic Sequence (Arithmetic Series) 125Estimation of Discharge Flow Rate during a

Well Control Event 126

chapter 9

129

Casing Wear

Casing Wear 129

chapter 10

137Narrow Margin DrillingChapter Introduction 137Responding to Narrow Margin Drilling Risks 138Well Design 139Mud Design 139

BHA Design 140Drilling Practices 140

chapter 11

143CementingChapter IntroductionBarriers 143Centralizer Stand-Off 151Estimation of OD of Cement Stingers for

Cement Plugs 152Estimation of Under-Displacement Volume if Stinger is Used to Set a Balance Plug 156

8162019 Drilling Operations Look Inside

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viiContents

chapter 12

159 Stuck Pipe Prevention and Recovery Chapter Introduction and Barriers 159Factors that Promote Differential Sticking 168Differential Sticking Potential 169Differential Stuck Pipe Recovery 171

chapter 13

177

Conductor Jetting

Chapter Introduction 177Bit Stick-Out 178Bit Space-Out 179Possibility of Reverse Jetting Angle for Stick Out Application (Upjet Nozzles) 181Comparison of Stick-Out and Space-Out 181Bit Drilled AreaHydraulically Jetted Area 182Calculation of Soak Time Required for

Conductor Casing 182Calculation of Jetted Conductor Forceto Buckling 184

Calculation of Force to Buckling in Drill Pipe 185

chapter 14

187Useful Drilling CalculationsMud Gas Separator 187Use of PWD 189Mud Compressibility 190Swab and Surge Pressures 195Estimation of Trip Margin 201Casing Slip Calculation 203Stretch Calculations 205Bit Pressure Loss 207Split FLow Between Bit and Reamer 208Kick Tolerance 227

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viii

chapter 15

233 Other Improvement Opportunities andMiscellaneous Drilling IssuesWell Trajectory Optimization 233Casing Running Improvement 240Optimizing Wellbore Monitoring 258Formation Integrity Test 261Annular Pressure Buildup 268

Glossary 283

Bibliography 305

Index 313

Contents

8162019 Drilling Operations Look Inside

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Acknowledgement

he author would like to thank his family his

friends and colleagues in the course of his

career whose valuable advices and experiences helped

achieved the goal of writing this book

Special thanks to Sheena Reuben who helped us

with the copyediting and proof reading of this book Te author dedicates this book to those who work

together safely and efficiently to deliver energy to the

world

8162019 Drilling Operations Look Inside

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Preface

O

ften drilling programs have documented

risks and mitigations against the identified

risks Although preventative actions against the iden-

tified risks may be expressed within the program the

emphasis is usually on the mitigation barriers against

the risks Hence it is not uncommon to see the termldquorisks and mitigationsrdquo in a drilling program Tis book

was born out of the desire to deliver the same risk man-

agement concept applied in chemical plants and refin-

eries into drilling planning and operations Barriers to

risk events should include preventative barriers and

mitigation barriers Mitigation barriers are reactive the

safety and cost of wells operations can be improved bycreating preventative barriers to reduce the chance of

the risk event occurring Mitigation barriers improve

the recovery time if a risk event should occur

8162019 Drilling Operations Look Inside

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Preface xi

Tis book focuses on improving drilling operations by managing bar-

riers (both preventative and mitigation) to risk events In Chapter 1 thebasic principles of risk management are described Te chapter talks about

everything from identification of risks to creating barriers (people process

procedures and equipment) for identified risks as well as steps to help

barrier creation Chapter 2 describes the process of drilling optimization

reviewing non-productive events from offset wells or other drilling cam-

paigns categorizing non-productive time events into those that increase

ldquodrilling timerdquo and those the extend ldquoflat timerdquo and barriers to be put inplace to optimize drilling operations Chapters 3 to 13 focus on common

non-productive time events such as loss circulation well control and so on

that lead to down-time in drilling operations and barriers to the risk events

as well as monitoringcontrol barrier (eg torque and drag) Useful drilling

calculations are highlighted in Chapter 14 Chapter 15 focuses on other

continuous improvement opportunities that are not covered in Chapters

2 through 13It is my desire that this book provides useful insight into drilling

operations improvements in the area of cost and risks It is a valuable

resource for anyone involved in well planning and operations engineers

and technicians preparing risk assessments and risk workbooks engineers

involved in writing drilling procedures engineers and managers reviewing

and approving drilling programs field engineers supervisors and superin-

tendents making decisions on the fly during drilling operations and also

students wishing to pursue careers in drilling engineering and operations

Although significant effort has been made to avoid errors they are

sometimes inevitable Suggestions towards the improvement of this book

are welcome

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CHAPTER

Risk ManagementBow-ties and theldquoPPErdquo Concept

E

very activity or operation in well construc-

tion has its own associated risk(s) Te cost of

running the operation will most certainly be impacted

by the level of risk that can be taken for that partic-

ular operation ypically the running of an operation

costs less if the level of risk associated with it is highand it is higher if the level of risk is lower However

any safety incidents arising out of high-risk opera-

tions could potentially lead to catastrophic damage

which in-turn may raise the overall cost of running

the operation immensely Terefore it is important

to identify all risks associated with any operation

during well construction and to determine what levelof risk is acceptable and to what extent Risk man-

agement is the economics of finding a suitable bal-

ance between running an operation by rejecting and

1

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Drilling Operations Cost and Risk Management 10

Table 11 Comparison of preventative and mitigation barriers

Preventative Barriers Mitigation Barriers

1 Proactive Reactive

2 Reduce the likelihood of an eventoccurring

Reduce the impact of an event

3 Involve elimination preventionand control

Involve mitigation and a recovery plan

4 Usually engineering design (welltrajectory design BHA designmud design) administrativeactions (eg enforcement ofbuffer zones) andor procedural(eg ensuring pipe movement toprevent differentially stuck pipe)

Personal and environmental protectionpersonal protective equipment (PPE)and Contingency plansproceduresCan also be engineering actions (egconstruction of berms for spill contain-ment) or administrative actions (egrestricting access to only essentialpersonnel during a well control event)

Figure 13 Bow-tie for stuck pipe

Causes

High Side ForceWelbore

Trajectory

Fluid LossAdditives

ReduceOverbalance

Jars in BottomHole Assembly

(BHA)

Stuck PipeContingency Plan

Sidetrack Plan

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Stuck PipeContingency Plan

Sidetrack Plan

Stuck PipeContingency Plan

Sidetrack Plan

Jars in BHA

Jars in BHA

StuckPipe

Hazard(Drilling)

Pull Pipe intoCasing when not

Rotating and

Circulating

Stabilizers inBHADrill Pipe

Protectors onon Drill Pipe

Control DoglegSeverity

FluidsPropertiesTracking

Contact Area

ExcessiveOverbalance

Event

ConsequenceMitigation BarriersPreventative Barriers

Use SpiralDrill Collars

in Bottom HoleAssembly (BHA)

adding fluid loss additive and filter cake reduction and using spiral

drill collars stabilizers and drill pipe protectors to minimize contact

areaControl Stuck pipe event can be controlled by creating a procedure that

ensures pipe movement during repairs for surface and downhole failures

when possible and also tracking fluid properties

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Drilling Operations Cost and Risk Management 16

Drilling optimization can be broken down into the following

bull Drilling time improvement Drilling time inefficiencies are factors

that affect the rate of penetration Examples are

use of the wrong drill bit for formation drilled

poor mud motorrotary steerable system tool selection

limitation of solid handling equipment

drill string vibrationbuckling

pump limitation for hole cleaning

drill string size causing high pump pressure unavailability or inadequate procedures for hole cleaning

data transfer limitation

bull Flat time reduction Flat time inefficiencies could be as a result of

events that change drilling time to flat time or events that extend flat

time Examples of events that change drilling time to flat time are

lost circulation

motor failure MWD (measurement while drilling) failure

bit failure

drill string failure

stuck pipe

well control

wellbore instability

failure of surface and downhole equipment casing wear

Examples of events that extend flat time are

suboptimal wellbore trajectoryhole tortuosity for casing run-

ning and logging ndash longer casing runninglogging time

swabsurge during casing running

excessive breaking circulationmud conditioning

inefficiency breaking circulation while running casingpipe

leading to losses

wellbore instability while drilling loggingrunning casing

excessive time to pull out of hole with drill string due to swab

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Drilling Operations Cost and Risk Management 22

review offset risks and the result of the offset analysis should be incorporated

into the new well design Te drilling engineerteam need to involve the

stakeholders right from the beginning of the planning process Drillingengineers should involve technical specialists other teamspeers as needed

Tey should involve vendors and suppliers too in order to utilize their

specialized knowledge new technology and database of offset wells since

Figure 27 Drilling optimization process flow

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Drilling Optimization 35

Power HP E WOB ROP

N T

m

b

( ) = times times times times( )

+ times times( ) + times

minus5 054 10

377 14 6 765 10

7

minusminus times times times times

3 2 2

4

ρ Q D ROP

d e

Where

E m = Mechanical efficiency ratio

MSE = Mechanical Specific Energy (psi)

Power Graph

bull Actual Data

r h

t

f P

O R

Desired region Low MSE High ROP

Undesired region High MSE Low ROP

200

180

160

140

120

100

80

6040

20

0

MSE kpsi

0 100 200 300 400 500 600 700 800

100 HP 200 HP 400 HP 800 HP 1000 HP

Figure 216 Power curve for a deep water well

(23)

Note Most data points fall in the desired region of high ROP low MSE and thetransition zone This is because ROP is not usually an issue because the rocksrsquocompressive strengths are lower in deep water than onshore For this particularwell pump relief valve set point as well as ECD limited the ability to increase the flowrate to clean the hole better to promote better transfer of energy to the bit (lowerwellbore friction) With improved hole cleaning if ECD andor pump pressure donot limit flow rate the data points in the transition zone could have moved to thedesired zone on the plot Real time vibration data did not suggest any issues dueto vibration

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Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

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Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

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8162019 Drilling Operations Look Inside

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A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 8: Drilling Operations Look Inside

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v

chapter 3

41 Vibration

Chapter Introduction 41 Typical Causes of Drill StringBHA Failure 53Drilling Torque Reduction Possible Solutions 54

chapter 4

57 Hole CleaningChapter IntroductionBarriers 57Back Reaming 62Sweeps 66Flow Rate for Hole Cleaning 67RPM for Hole Cleaning 68Cuttings Carrying Index 70

chapter 5

75 Torque and Drag

Chapter introduction 75Drilling Torque Reduction Technique 78

chapter 6

81

Drilling Fluid Properties Maintenance

Fluid Properties Maintenance 81Barite Sag 87

chapter 7

89Wellbore Stability and LostCirculationChapter Introduction 89Wellbore Stability 89Factors affecting Wellbore Stability 93Estimation of Flow Rate Required to

Maintain Annular Velocity in Washed Hole 97

Contents

8162019 Drilling Operations Look Inside

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Contents vi

chapter 8

113 Well ControlChapter IntroductionBarriers 113Riser Disconnect 117Increase in Mud Weight to Disconnect the Riser (Riser Margin) 118Estimation of Trip Margin 119Shallow GasWater 120Estimating Weight and Volume of Pump and

Dump Mud 124Using Integration Method 125Sum of Arithmetic Sequence (Arithmetic Series) 125Estimation of Discharge Flow Rate during a

Well Control Event 126

chapter 9

129

Casing Wear

Casing Wear 129

chapter 10

137Narrow Margin DrillingChapter Introduction 137Responding to Narrow Margin Drilling Risks 138Well Design 139Mud Design 139

BHA Design 140Drilling Practices 140

chapter 11

143CementingChapter IntroductionBarriers 143Centralizer Stand-Off 151Estimation of OD of Cement Stingers for

Cement Plugs 152Estimation of Under-Displacement Volume if Stinger is Used to Set a Balance Plug 156

8162019 Drilling Operations Look Inside

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viiContents

chapter 12

159 Stuck Pipe Prevention and Recovery Chapter Introduction and Barriers 159Factors that Promote Differential Sticking 168Differential Sticking Potential 169Differential Stuck Pipe Recovery 171

chapter 13

177

Conductor Jetting

Chapter Introduction 177Bit Stick-Out 178Bit Space-Out 179Possibility of Reverse Jetting Angle for Stick Out Application (Upjet Nozzles) 181Comparison of Stick-Out and Space-Out 181Bit Drilled AreaHydraulically Jetted Area 182Calculation of Soak Time Required for

Conductor Casing 182Calculation of Jetted Conductor Forceto Buckling 184

Calculation of Force to Buckling in Drill Pipe 185

chapter 14

187Useful Drilling CalculationsMud Gas Separator 187Use of PWD 189Mud Compressibility 190Swab and Surge Pressures 195Estimation of Trip Margin 201Casing Slip Calculation 203Stretch Calculations 205Bit Pressure Loss 207Split FLow Between Bit and Reamer 208Kick Tolerance 227

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viii

chapter 15

233 Other Improvement Opportunities andMiscellaneous Drilling IssuesWell Trajectory Optimization 233Casing Running Improvement 240Optimizing Wellbore Monitoring 258Formation Integrity Test 261Annular Pressure Buildup 268

Glossary 283

Bibliography 305

Index 313

Contents

8162019 Drilling Operations Look Inside

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Acknowledgement

he author would like to thank his family his

friends and colleagues in the course of his

career whose valuable advices and experiences helped

achieved the goal of writing this book

Special thanks to Sheena Reuben who helped us

with the copyediting and proof reading of this book Te author dedicates this book to those who work

together safely and efficiently to deliver energy to the

world

8162019 Drilling Operations Look Inside

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Preface

O

ften drilling programs have documented

risks and mitigations against the identified

risks Although preventative actions against the iden-

tified risks may be expressed within the program the

emphasis is usually on the mitigation barriers against

the risks Hence it is not uncommon to see the termldquorisks and mitigationsrdquo in a drilling program Tis book

was born out of the desire to deliver the same risk man-

agement concept applied in chemical plants and refin-

eries into drilling planning and operations Barriers to

risk events should include preventative barriers and

mitigation barriers Mitigation barriers are reactive the

safety and cost of wells operations can be improved bycreating preventative barriers to reduce the chance of

the risk event occurring Mitigation barriers improve

the recovery time if a risk event should occur

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Preface xi

Tis book focuses on improving drilling operations by managing bar-

riers (both preventative and mitigation) to risk events In Chapter 1 thebasic principles of risk management are described Te chapter talks about

everything from identification of risks to creating barriers (people process

procedures and equipment) for identified risks as well as steps to help

barrier creation Chapter 2 describes the process of drilling optimization

reviewing non-productive events from offset wells or other drilling cam-

paigns categorizing non-productive time events into those that increase

ldquodrilling timerdquo and those the extend ldquoflat timerdquo and barriers to be put inplace to optimize drilling operations Chapters 3 to 13 focus on common

non-productive time events such as loss circulation well control and so on

that lead to down-time in drilling operations and barriers to the risk events

as well as monitoringcontrol barrier (eg torque and drag) Useful drilling

calculations are highlighted in Chapter 14 Chapter 15 focuses on other

continuous improvement opportunities that are not covered in Chapters

2 through 13It is my desire that this book provides useful insight into drilling

operations improvements in the area of cost and risks It is a valuable

resource for anyone involved in well planning and operations engineers

and technicians preparing risk assessments and risk workbooks engineers

involved in writing drilling procedures engineers and managers reviewing

and approving drilling programs field engineers supervisors and superin-

tendents making decisions on the fly during drilling operations and also

students wishing to pursue careers in drilling engineering and operations

Although significant effort has been made to avoid errors they are

sometimes inevitable Suggestions towards the improvement of this book

are welcome

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CHAPTER

Risk ManagementBow-ties and theldquoPPErdquo Concept

E

very activity or operation in well construc-

tion has its own associated risk(s) Te cost of

running the operation will most certainly be impacted

by the level of risk that can be taken for that partic-

ular operation ypically the running of an operation

costs less if the level of risk associated with it is highand it is higher if the level of risk is lower However

any safety incidents arising out of high-risk opera-

tions could potentially lead to catastrophic damage

which in-turn may raise the overall cost of running

the operation immensely Terefore it is important

to identify all risks associated with any operation

during well construction and to determine what levelof risk is acceptable and to what extent Risk man-

agement is the economics of finding a suitable bal-

ance between running an operation by rejecting and

1

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Drilling Operations Cost and Risk Management 10

Table 11 Comparison of preventative and mitigation barriers

Preventative Barriers Mitigation Barriers

1 Proactive Reactive

2 Reduce the likelihood of an eventoccurring

Reduce the impact of an event

3 Involve elimination preventionand control

Involve mitigation and a recovery plan

4 Usually engineering design (welltrajectory design BHA designmud design) administrativeactions (eg enforcement ofbuffer zones) andor procedural(eg ensuring pipe movement toprevent differentially stuck pipe)

Personal and environmental protectionpersonal protective equipment (PPE)and Contingency plansproceduresCan also be engineering actions (egconstruction of berms for spill contain-ment) or administrative actions (egrestricting access to only essentialpersonnel during a well control event)

Figure 13 Bow-tie for stuck pipe

Causes

High Side ForceWelbore

Trajectory

Fluid LossAdditives

ReduceOverbalance

Jars in BottomHole Assembly

(BHA)

Stuck PipeContingency Plan

Sidetrack Plan

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Stuck PipeContingency Plan

Sidetrack Plan

Stuck PipeContingency Plan

Sidetrack Plan

Jars in BHA

Jars in BHA

StuckPipe

Hazard(Drilling)

Pull Pipe intoCasing when not

Rotating and

Circulating

Stabilizers inBHADrill Pipe

Protectors onon Drill Pipe

Control DoglegSeverity

FluidsPropertiesTracking

Contact Area

ExcessiveOverbalance

Event

ConsequenceMitigation BarriersPreventative Barriers

Use SpiralDrill Collars

in Bottom HoleAssembly (BHA)

adding fluid loss additive and filter cake reduction and using spiral

drill collars stabilizers and drill pipe protectors to minimize contact

areaControl Stuck pipe event can be controlled by creating a procedure that

ensures pipe movement during repairs for surface and downhole failures

when possible and also tracking fluid properties

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Drilling Operations Cost and Risk Management 16

Drilling optimization can be broken down into the following

bull Drilling time improvement Drilling time inefficiencies are factors

that affect the rate of penetration Examples are

use of the wrong drill bit for formation drilled

poor mud motorrotary steerable system tool selection

limitation of solid handling equipment

drill string vibrationbuckling

pump limitation for hole cleaning

drill string size causing high pump pressure unavailability or inadequate procedures for hole cleaning

data transfer limitation

bull Flat time reduction Flat time inefficiencies could be as a result of

events that change drilling time to flat time or events that extend flat

time Examples of events that change drilling time to flat time are

lost circulation

motor failure MWD (measurement while drilling) failure

bit failure

drill string failure

stuck pipe

well control

wellbore instability

failure of surface and downhole equipment casing wear

Examples of events that extend flat time are

suboptimal wellbore trajectoryhole tortuosity for casing run-

ning and logging ndash longer casing runninglogging time

swabsurge during casing running

excessive breaking circulationmud conditioning

inefficiency breaking circulation while running casingpipe

leading to losses

wellbore instability while drilling loggingrunning casing

excessive time to pull out of hole with drill string due to swab

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Drilling Operations Cost and Risk Management 22

review offset risks and the result of the offset analysis should be incorporated

into the new well design Te drilling engineerteam need to involve the

stakeholders right from the beginning of the planning process Drillingengineers should involve technical specialists other teamspeers as needed

Tey should involve vendors and suppliers too in order to utilize their

specialized knowledge new technology and database of offset wells since

Figure 27 Drilling optimization process flow

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Drilling Optimization 35

Power HP E WOB ROP

N T

m

b

( ) = times times times times( )

+ times times( ) + times

minus5 054 10

377 14 6 765 10

7

minusminus times times times times

3 2 2

4

ρ Q D ROP

d e

Where

E m = Mechanical efficiency ratio

MSE = Mechanical Specific Energy (psi)

Power Graph

bull Actual Data

r h

t

f P

O R

Desired region Low MSE High ROP

Undesired region High MSE Low ROP

200

180

160

140

120

100

80

6040

20

0

MSE kpsi

0 100 200 300 400 500 600 700 800

100 HP 200 HP 400 HP 800 HP 1000 HP

Figure 216 Power curve for a deep water well

(23)

Note Most data points fall in the desired region of high ROP low MSE and thetransition zone This is because ROP is not usually an issue because the rocksrsquocompressive strengths are lower in deep water than onshore For this particularwell pump relief valve set point as well as ECD limited the ability to increase the flowrate to clean the hole better to promote better transfer of energy to the bit (lowerwellbore friction) With improved hole cleaning if ECD andor pump pressure donot limit flow rate the data points in the transition zone could have moved to thedesired zone on the plot Real time vibration data did not suggest any issues dueto vibration

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Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

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Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

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8162019 Drilling Operations Look Inside

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A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 9: Drilling Operations Look Inside

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Contents vi

chapter 8

113 Well ControlChapter IntroductionBarriers 113Riser Disconnect 117Increase in Mud Weight to Disconnect the Riser (Riser Margin) 118Estimation of Trip Margin 119Shallow GasWater 120Estimating Weight and Volume of Pump and

Dump Mud 124Using Integration Method 125Sum of Arithmetic Sequence (Arithmetic Series) 125Estimation of Discharge Flow Rate during a

Well Control Event 126

chapter 9

129

Casing Wear

Casing Wear 129

chapter 10

137Narrow Margin DrillingChapter Introduction 137Responding to Narrow Margin Drilling Risks 138Well Design 139Mud Design 139

BHA Design 140Drilling Practices 140

chapter 11

143CementingChapter IntroductionBarriers 143Centralizer Stand-Off 151Estimation of OD of Cement Stingers for

Cement Plugs 152Estimation of Under-Displacement Volume if Stinger is Used to Set a Balance Plug 156

8162019 Drilling Operations Look Inside

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viiContents

chapter 12

159 Stuck Pipe Prevention and Recovery Chapter Introduction and Barriers 159Factors that Promote Differential Sticking 168Differential Sticking Potential 169Differential Stuck Pipe Recovery 171

chapter 13

177

Conductor Jetting

Chapter Introduction 177Bit Stick-Out 178Bit Space-Out 179Possibility of Reverse Jetting Angle for Stick Out Application (Upjet Nozzles) 181Comparison of Stick-Out and Space-Out 181Bit Drilled AreaHydraulically Jetted Area 182Calculation of Soak Time Required for

Conductor Casing 182Calculation of Jetted Conductor Forceto Buckling 184

Calculation of Force to Buckling in Drill Pipe 185

chapter 14

187Useful Drilling CalculationsMud Gas Separator 187Use of PWD 189Mud Compressibility 190Swab and Surge Pressures 195Estimation of Trip Margin 201Casing Slip Calculation 203Stretch Calculations 205Bit Pressure Loss 207Split FLow Between Bit and Reamer 208Kick Tolerance 227

8162019 Drilling Operations Look Inside

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viii

chapter 15

233 Other Improvement Opportunities andMiscellaneous Drilling IssuesWell Trajectory Optimization 233Casing Running Improvement 240Optimizing Wellbore Monitoring 258Formation Integrity Test 261Annular Pressure Buildup 268

Glossary 283

Bibliography 305

Index 313

Contents

8162019 Drilling Operations Look Inside

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Acknowledgement

he author would like to thank his family his

friends and colleagues in the course of his

career whose valuable advices and experiences helped

achieved the goal of writing this book

Special thanks to Sheena Reuben who helped us

with the copyediting and proof reading of this book Te author dedicates this book to those who work

together safely and efficiently to deliver energy to the

world

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Preface

O

ften drilling programs have documented

risks and mitigations against the identified

risks Although preventative actions against the iden-

tified risks may be expressed within the program the

emphasis is usually on the mitigation barriers against

the risks Hence it is not uncommon to see the termldquorisks and mitigationsrdquo in a drilling program Tis book

was born out of the desire to deliver the same risk man-

agement concept applied in chemical plants and refin-

eries into drilling planning and operations Barriers to

risk events should include preventative barriers and

mitigation barriers Mitigation barriers are reactive the

safety and cost of wells operations can be improved bycreating preventative barriers to reduce the chance of

the risk event occurring Mitigation barriers improve

the recovery time if a risk event should occur

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Preface xi

Tis book focuses on improving drilling operations by managing bar-

riers (both preventative and mitigation) to risk events In Chapter 1 thebasic principles of risk management are described Te chapter talks about

everything from identification of risks to creating barriers (people process

procedures and equipment) for identified risks as well as steps to help

barrier creation Chapter 2 describes the process of drilling optimization

reviewing non-productive events from offset wells or other drilling cam-

paigns categorizing non-productive time events into those that increase

ldquodrilling timerdquo and those the extend ldquoflat timerdquo and barriers to be put inplace to optimize drilling operations Chapters 3 to 13 focus on common

non-productive time events such as loss circulation well control and so on

that lead to down-time in drilling operations and barriers to the risk events

as well as monitoringcontrol barrier (eg torque and drag) Useful drilling

calculations are highlighted in Chapter 14 Chapter 15 focuses on other

continuous improvement opportunities that are not covered in Chapters

2 through 13It is my desire that this book provides useful insight into drilling

operations improvements in the area of cost and risks It is a valuable

resource for anyone involved in well planning and operations engineers

and technicians preparing risk assessments and risk workbooks engineers

involved in writing drilling procedures engineers and managers reviewing

and approving drilling programs field engineers supervisors and superin-

tendents making decisions on the fly during drilling operations and also

students wishing to pursue careers in drilling engineering and operations

Although significant effort has been made to avoid errors they are

sometimes inevitable Suggestions towards the improvement of this book

are welcome

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CHAPTER

Risk ManagementBow-ties and theldquoPPErdquo Concept

E

very activity or operation in well construc-

tion has its own associated risk(s) Te cost of

running the operation will most certainly be impacted

by the level of risk that can be taken for that partic-

ular operation ypically the running of an operation

costs less if the level of risk associated with it is highand it is higher if the level of risk is lower However

any safety incidents arising out of high-risk opera-

tions could potentially lead to catastrophic damage

which in-turn may raise the overall cost of running

the operation immensely Terefore it is important

to identify all risks associated with any operation

during well construction and to determine what levelof risk is acceptable and to what extent Risk man-

agement is the economics of finding a suitable bal-

ance between running an operation by rejecting and

1

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Drilling Operations Cost and Risk Management 10

Table 11 Comparison of preventative and mitigation barriers

Preventative Barriers Mitigation Barriers

1 Proactive Reactive

2 Reduce the likelihood of an eventoccurring

Reduce the impact of an event

3 Involve elimination preventionand control

Involve mitigation and a recovery plan

4 Usually engineering design (welltrajectory design BHA designmud design) administrativeactions (eg enforcement ofbuffer zones) andor procedural(eg ensuring pipe movement toprevent differentially stuck pipe)

Personal and environmental protectionpersonal protective equipment (PPE)and Contingency plansproceduresCan also be engineering actions (egconstruction of berms for spill contain-ment) or administrative actions (egrestricting access to only essentialpersonnel during a well control event)

Figure 13 Bow-tie for stuck pipe

Causes

High Side ForceWelbore

Trajectory

Fluid LossAdditives

ReduceOverbalance

Jars in BottomHole Assembly

(BHA)

Stuck PipeContingency Plan

Sidetrack Plan

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Stuck PipeContingency Plan

Sidetrack Plan

Stuck PipeContingency Plan

Sidetrack Plan

Jars in BHA

Jars in BHA

StuckPipe

Hazard(Drilling)

Pull Pipe intoCasing when not

Rotating and

Circulating

Stabilizers inBHADrill Pipe

Protectors onon Drill Pipe

Control DoglegSeverity

FluidsPropertiesTracking

Contact Area

ExcessiveOverbalance

Event

ConsequenceMitigation BarriersPreventative Barriers

Use SpiralDrill Collars

in Bottom HoleAssembly (BHA)

adding fluid loss additive and filter cake reduction and using spiral

drill collars stabilizers and drill pipe protectors to minimize contact

areaControl Stuck pipe event can be controlled by creating a procedure that

ensures pipe movement during repairs for surface and downhole failures

when possible and also tracking fluid properties

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Drilling Operations Cost and Risk Management 16

Drilling optimization can be broken down into the following

bull Drilling time improvement Drilling time inefficiencies are factors

that affect the rate of penetration Examples are

use of the wrong drill bit for formation drilled

poor mud motorrotary steerable system tool selection

limitation of solid handling equipment

drill string vibrationbuckling

pump limitation for hole cleaning

drill string size causing high pump pressure unavailability or inadequate procedures for hole cleaning

data transfer limitation

bull Flat time reduction Flat time inefficiencies could be as a result of

events that change drilling time to flat time or events that extend flat

time Examples of events that change drilling time to flat time are

lost circulation

motor failure MWD (measurement while drilling) failure

bit failure

drill string failure

stuck pipe

well control

wellbore instability

failure of surface and downhole equipment casing wear

Examples of events that extend flat time are

suboptimal wellbore trajectoryhole tortuosity for casing run-

ning and logging ndash longer casing runninglogging time

swabsurge during casing running

excessive breaking circulationmud conditioning

inefficiency breaking circulation while running casingpipe

leading to losses

wellbore instability while drilling loggingrunning casing

excessive time to pull out of hole with drill string due to swab

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Drilling Operations Cost and Risk Management 22

review offset risks and the result of the offset analysis should be incorporated

into the new well design Te drilling engineerteam need to involve the

stakeholders right from the beginning of the planning process Drillingengineers should involve technical specialists other teamspeers as needed

Tey should involve vendors and suppliers too in order to utilize their

specialized knowledge new technology and database of offset wells since

Figure 27 Drilling optimization process flow

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Drilling Optimization 35

Power HP E WOB ROP

N T

m

b

( ) = times times times times( )

+ times times( ) + times

minus5 054 10

377 14 6 765 10

7

minusminus times times times times

3 2 2

4

ρ Q D ROP

d e

Where

E m = Mechanical efficiency ratio

MSE = Mechanical Specific Energy (psi)

Power Graph

bull Actual Data

r h

t

f P

O R

Desired region Low MSE High ROP

Undesired region High MSE Low ROP

200

180

160

140

120

100

80

6040

20

0

MSE kpsi

0 100 200 300 400 500 600 700 800

100 HP 200 HP 400 HP 800 HP 1000 HP

Figure 216 Power curve for a deep water well

(23)

Note Most data points fall in the desired region of high ROP low MSE and thetransition zone This is because ROP is not usually an issue because the rocksrsquocompressive strengths are lower in deep water than onshore For this particularwell pump relief valve set point as well as ECD limited the ability to increase the flowrate to clean the hole better to promote better transfer of energy to the bit (lowerwellbore friction) With improved hole cleaning if ECD andor pump pressure donot limit flow rate the data points in the transition zone could have moved to thedesired zone on the plot Real time vibration data did not suggest any issues dueto vibration

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Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

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Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

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8162019 Drilling Operations Look Inside

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A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 10: Drilling Operations Look Inside

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viiContents

chapter 12

159 Stuck Pipe Prevention and Recovery Chapter Introduction and Barriers 159Factors that Promote Differential Sticking 168Differential Sticking Potential 169Differential Stuck Pipe Recovery 171

chapter 13

177

Conductor Jetting

Chapter Introduction 177Bit Stick-Out 178Bit Space-Out 179Possibility of Reverse Jetting Angle for Stick Out Application (Upjet Nozzles) 181Comparison of Stick-Out and Space-Out 181Bit Drilled AreaHydraulically Jetted Area 182Calculation of Soak Time Required for

Conductor Casing 182Calculation of Jetted Conductor Forceto Buckling 184

Calculation of Force to Buckling in Drill Pipe 185

chapter 14

187Useful Drilling CalculationsMud Gas Separator 187Use of PWD 189Mud Compressibility 190Swab and Surge Pressures 195Estimation of Trip Margin 201Casing Slip Calculation 203Stretch Calculations 205Bit Pressure Loss 207Split FLow Between Bit and Reamer 208Kick Tolerance 227

8162019 Drilling Operations Look Inside

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viii

chapter 15

233 Other Improvement Opportunities andMiscellaneous Drilling IssuesWell Trajectory Optimization 233Casing Running Improvement 240Optimizing Wellbore Monitoring 258Formation Integrity Test 261Annular Pressure Buildup 268

Glossary 283

Bibliography 305

Index 313

Contents

8162019 Drilling Operations Look Inside

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Acknowledgement

he author would like to thank his family his

friends and colleagues in the course of his

career whose valuable advices and experiences helped

achieved the goal of writing this book

Special thanks to Sheena Reuben who helped us

with the copyediting and proof reading of this book Te author dedicates this book to those who work

together safely and efficiently to deliver energy to the

world

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 1333

Preface

O

ften drilling programs have documented

risks and mitigations against the identified

risks Although preventative actions against the iden-

tified risks may be expressed within the program the

emphasis is usually on the mitigation barriers against

the risks Hence it is not uncommon to see the termldquorisks and mitigationsrdquo in a drilling program Tis book

was born out of the desire to deliver the same risk man-

agement concept applied in chemical plants and refin-

eries into drilling planning and operations Barriers to

risk events should include preventative barriers and

mitigation barriers Mitigation barriers are reactive the

safety and cost of wells operations can be improved bycreating preventative barriers to reduce the chance of

the risk event occurring Mitigation barriers improve

the recovery time if a risk event should occur

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Preface xi

Tis book focuses on improving drilling operations by managing bar-

riers (both preventative and mitigation) to risk events In Chapter 1 thebasic principles of risk management are described Te chapter talks about

everything from identification of risks to creating barriers (people process

procedures and equipment) for identified risks as well as steps to help

barrier creation Chapter 2 describes the process of drilling optimization

reviewing non-productive events from offset wells or other drilling cam-

paigns categorizing non-productive time events into those that increase

ldquodrilling timerdquo and those the extend ldquoflat timerdquo and barriers to be put inplace to optimize drilling operations Chapters 3 to 13 focus on common

non-productive time events such as loss circulation well control and so on

that lead to down-time in drilling operations and barriers to the risk events

as well as monitoringcontrol barrier (eg torque and drag) Useful drilling

calculations are highlighted in Chapter 14 Chapter 15 focuses on other

continuous improvement opportunities that are not covered in Chapters

2 through 13It is my desire that this book provides useful insight into drilling

operations improvements in the area of cost and risks It is a valuable

resource for anyone involved in well planning and operations engineers

and technicians preparing risk assessments and risk workbooks engineers

involved in writing drilling procedures engineers and managers reviewing

and approving drilling programs field engineers supervisors and superin-

tendents making decisions on the fly during drilling operations and also

students wishing to pursue careers in drilling engineering and operations

Although significant effort has been made to avoid errors they are

sometimes inevitable Suggestions towards the improvement of this book

are welcome

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8162019 Drilling Operations Look Inside

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CHAPTER

Risk ManagementBow-ties and theldquoPPErdquo Concept

E

very activity or operation in well construc-

tion has its own associated risk(s) Te cost of

running the operation will most certainly be impacted

by the level of risk that can be taken for that partic-

ular operation ypically the running of an operation

costs less if the level of risk associated with it is highand it is higher if the level of risk is lower However

any safety incidents arising out of high-risk opera-

tions could potentially lead to catastrophic damage

which in-turn may raise the overall cost of running

the operation immensely Terefore it is important

to identify all risks associated with any operation

during well construction and to determine what levelof risk is acceptable and to what extent Risk man-

agement is the economics of finding a suitable bal-

ance between running an operation by rejecting and

1

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Drilling Operations Cost and Risk Management 10

Table 11 Comparison of preventative and mitigation barriers

Preventative Barriers Mitigation Barriers

1 Proactive Reactive

2 Reduce the likelihood of an eventoccurring

Reduce the impact of an event

3 Involve elimination preventionand control

Involve mitigation and a recovery plan

4 Usually engineering design (welltrajectory design BHA designmud design) administrativeactions (eg enforcement ofbuffer zones) andor procedural(eg ensuring pipe movement toprevent differentially stuck pipe)

Personal and environmental protectionpersonal protective equipment (PPE)and Contingency plansproceduresCan also be engineering actions (egconstruction of berms for spill contain-ment) or administrative actions (egrestricting access to only essentialpersonnel during a well control event)

Figure 13 Bow-tie for stuck pipe

Causes

High Side ForceWelbore

Trajectory

Fluid LossAdditives

ReduceOverbalance

Jars in BottomHole Assembly

(BHA)

Stuck PipeContingency Plan

Sidetrack Plan

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Stuck PipeContingency Plan

Sidetrack Plan

Stuck PipeContingency Plan

Sidetrack Plan

Jars in BHA

Jars in BHA

StuckPipe

Hazard(Drilling)

Pull Pipe intoCasing when not

Rotating and

Circulating

Stabilizers inBHADrill Pipe

Protectors onon Drill Pipe

Control DoglegSeverity

FluidsPropertiesTracking

Contact Area

ExcessiveOverbalance

Event

ConsequenceMitigation BarriersPreventative Barriers

Use SpiralDrill Collars

in Bottom HoleAssembly (BHA)

adding fluid loss additive and filter cake reduction and using spiral

drill collars stabilizers and drill pipe protectors to minimize contact

areaControl Stuck pipe event can be controlled by creating a procedure that

ensures pipe movement during repairs for surface and downhole failures

when possible and also tracking fluid properties

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Drilling Operations Cost and Risk Management 16

Drilling optimization can be broken down into the following

bull Drilling time improvement Drilling time inefficiencies are factors

that affect the rate of penetration Examples are

use of the wrong drill bit for formation drilled

poor mud motorrotary steerable system tool selection

limitation of solid handling equipment

drill string vibrationbuckling

pump limitation for hole cleaning

drill string size causing high pump pressure unavailability or inadequate procedures for hole cleaning

data transfer limitation

bull Flat time reduction Flat time inefficiencies could be as a result of

events that change drilling time to flat time or events that extend flat

time Examples of events that change drilling time to flat time are

lost circulation

motor failure MWD (measurement while drilling) failure

bit failure

drill string failure

stuck pipe

well control

wellbore instability

failure of surface and downhole equipment casing wear

Examples of events that extend flat time are

suboptimal wellbore trajectoryhole tortuosity for casing run-

ning and logging ndash longer casing runninglogging time

swabsurge during casing running

excessive breaking circulationmud conditioning

inefficiency breaking circulation while running casingpipe

leading to losses

wellbore instability while drilling loggingrunning casing

excessive time to pull out of hole with drill string due to swab

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Drilling Operations Cost and Risk Management 22

review offset risks and the result of the offset analysis should be incorporated

into the new well design Te drilling engineerteam need to involve the

stakeholders right from the beginning of the planning process Drillingengineers should involve technical specialists other teamspeers as needed

Tey should involve vendors and suppliers too in order to utilize their

specialized knowledge new technology and database of offset wells since

Figure 27 Drilling optimization process flow

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Drilling Optimization 35

Power HP E WOB ROP

N T

m

b

( ) = times times times times( )

+ times times( ) + times

minus5 054 10

377 14 6 765 10

7

minusminus times times times times

3 2 2

4

ρ Q D ROP

d e

Where

E m = Mechanical efficiency ratio

MSE = Mechanical Specific Energy (psi)

Power Graph

bull Actual Data

r h

t

f P

O R

Desired region Low MSE High ROP

Undesired region High MSE Low ROP

200

180

160

140

120

100

80

6040

20

0

MSE kpsi

0 100 200 300 400 500 600 700 800

100 HP 200 HP 400 HP 800 HP 1000 HP

Figure 216 Power curve for a deep water well

(23)

Note Most data points fall in the desired region of high ROP low MSE and thetransition zone This is because ROP is not usually an issue because the rocksrsquocompressive strengths are lower in deep water than onshore For this particularwell pump relief valve set point as well as ECD limited the ability to increase the flowrate to clean the hole better to promote better transfer of energy to the bit (lowerwellbore friction) With improved hole cleaning if ECD andor pump pressure donot limit flow rate the data points in the transition zone could have moved to thedesired zone on the plot Real time vibration data did not suggest any issues dueto vibration

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Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

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Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

8162019 Drilling Operations Look Inside

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8162019 Drilling Operations Look Inside

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A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 11: Drilling Operations Look Inside

8162019 Drilling Operations Look Inside

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viii

chapter 15

233 Other Improvement Opportunities andMiscellaneous Drilling IssuesWell Trajectory Optimization 233Casing Running Improvement 240Optimizing Wellbore Monitoring 258Formation Integrity Test 261Annular Pressure Buildup 268

Glossary 283

Bibliography 305

Index 313

Contents

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 1233

Acknowledgement

he author would like to thank his family his

friends and colleagues in the course of his

career whose valuable advices and experiences helped

achieved the goal of writing this book

Special thanks to Sheena Reuben who helped us

with the copyediting and proof reading of this book Te author dedicates this book to those who work

together safely and efficiently to deliver energy to the

world

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 1333

Preface

O

ften drilling programs have documented

risks and mitigations against the identified

risks Although preventative actions against the iden-

tified risks may be expressed within the program the

emphasis is usually on the mitigation barriers against

the risks Hence it is not uncommon to see the termldquorisks and mitigationsrdquo in a drilling program Tis book

was born out of the desire to deliver the same risk man-

agement concept applied in chemical plants and refin-

eries into drilling planning and operations Barriers to

risk events should include preventative barriers and

mitigation barriers Mitigation barriers are reactive the

safety and cost of wells operations can be improved bycreating preventative barriers to reduce the chance of

the risk event occurring Mitigation barriers improve

the recovery time if a risk event should occur

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 1433

Preface xi

Tis book focuses on improving drilling operations by managing bar-

riers (both preventative and mitigation) to risk events In Chapter 1 thebasic principles of risk management are described Te chapter talks about

everything from identification of risks to creating barriers (people process

procedures and equipment) for identified risks as well as steps to help

barrier creation Chapter 2 describes the process of drilling optimization

reviewing non-productive events from offset wells or other drilling cam-

paigns categorizing non-productive time events into those that increase

ldquodrilling timerdquo and those the extend ldquoflat timerdquo and barriers to be put inplace to optimize drilling operations Chapters 3 to 13 focus on common

non-productive time events such as loss circulation well control and so on

that lead to down-time in drilling operations and barriers to the risk events

as well as monitoringcontrol barrier (eg torque and drag) Useful drilling

calculations are highlighted in Chapter 14 Chapter 15 focuses on other

continuous improvement opportunities that are not covered in Chapters

2 through 13It is my desire that this book provides useful insight into drilling

operations improvements in the area of cost and risks It is a valuable

resource for anyone involved in well planning and operations engineers

and technicians preparing risk assessments and risk workbooks engineers

involved in writing drilling procedures engineers and managers reviewing

and approving drilling programs field engineers supervisors and superin-

tendents making decisions on the fly during drilling operations and also

students wishing to pursue careers in drilling engineering and operations

Although significant effort has been made to avoid errors they are

sometimes inevitable Suggestions towards the improvement of this book

are welcome

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CHAPTER

Risk ManagementBow-ties and theldquoPPErdquo Concept

E

very activity or operation in well construc-

tion has its own associated risk(s) Te cost of

running the operation will most certainly be impacted

by the level of risk that can be taken for that partic-

ular operation ypically the running of an operation

costs less if the level of risk associated with it is highand it is higher if the level of risk is lower However

any safety incidents arising out of high-risk opera-

tions could potentially lead to catastrophic damage

which in-turn may raise the overall cost of running

the operation immensely Terefore it is important

to identify all risks associated with any operation

during well construction and to determine what levelof risk is acceptable and to what extent Risk man-

agement is the economics of finding a suitable bal-

ance between running an operation by rejecting and

1

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Drilling Operations Cost and Risk Management 10

Table 11 Comparison of preventative and mitigation barriers

Preventative Barriers Mitigation Barriers

1 Proactive Reactive

2 Reduce the likelihood of an eventoccurring

Reduce the impact of an event

3 Involve elimination preventionand control

Involve mitigation and a recovery plan

4 Usually engineering design (welltrajectory design BHA designmud design) administrativeactions (eg enforcement ofbuffer zones) andor procedural(eg ensuring pipe movement toprevent differentially stuck pipe)

Personal and environmental protectionpersonal protective equipment (PPE)and Contingency plansproceduresCan also be engineering actions (egconstruction of berms for spill contain-ment) or administrative actions (egrestricting access to only essentialpersonnel during a well control event)

Figure 13 Bow-tie for stuck pipe

Causes

High Side ForceWelbore

Trajectory

Fluid LossAdditives

ReduceOverbalance

Jars in BottomHole Assembly

(BHA)

Stuck PipeContingency Plan

Sidetrack Plan

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Stuck PipeContingency Plan

Sidetrack Plan

Stuck PipeContingency Plan

Sidetrack Plan

Jars in BHA

Jars in BHA

StuckPipe

Hazard(Drilling)

Pull Pipe intoCasing when not

Rotating and

Circulating

Stabilizers inBHADrill Pipe

Protectors onon Drill Pipe

Control DoglegSeverity

FluidsPropertiesTracking

Contact Area

ExcessiveOverbalance

Event

ConsequenceMitigation BarriersPreventative Barriers

Use SpiralDrill Collars

in Bottom HoleAssembly (BHA)

adding fluid loss additive and filter cake reduction and using spiral

drill collars stabilizers and drill pipe protectors to minimize contact

areaControl Stuck pipe event can be controlled by creating a procedure that

ensures pipe movement during repairs for surface and downhole failures

when possible and also tracking fluid properties

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Drilling Operations Cost and Risk Management 16

Drilling optimization can be broken down into the following

bull Drilling time improvement Drilling time inefficiencies are factors

that affect the rate of penetration Examples are

use of the wrong drill bit for formation drilled

poor mud motorrotary steerable system tool selection

limitation of solid handling equipment

drill string vibrationbuckling

pump limitation for hole cleaning

drill string size causing high pump pressure unavailability or inadequate procedures for hole cleaning

data transfer limitation

bull Flat time reduction Flat time inefficiencies could be as a result of

events that change drilling time to flat time or events that extend flat

time Examples of events that change drilling time to flat time are

lost circulation

motor failure MWD (measurement while drilling) failure

bit failure

drill string failure

stuck pipe

well control

wellbore instability

failure of surface and downhole equipment casing wear

Examples of events that extend flat time are

suboptimal wellbore trajectoryhole tortuosity for casing run-

ning and logging ndash longer casing runninglogging time

swabsurge during casing running

excessive breaking circulationmud conditioning

inefficiency breaking circulation while running casingpipe

leading to losses

wellbore instability while drilling loggingrunning casing

excessive time to pull out of hole with drill string due to swab

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Drilling Operations Cost and Risk Management 22

review offset risks and the result of the offset analysis should be incorporated

into the new well design Te drilling engineerteam need to involve the

stakeholders right from the beginning of the planning process Drillingengineers should involve technical specialists other teamspeers as needed

Tey should involve vendors and suppliers too in order to utilize their

specialized knowledge new technology and database of offset wells since

Figure 27 Drilling optimization process flow

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Drilling Optimization 35

Power HP E WOB ROP

N T

m

b

( ) = times times times times( )

+ times times( ) + times

minus5 054 10

377 14 6 765 10

7

minusminus times times times times

3 2 2

4

ρ Q D ROP

d e

Where

E m = Mechanical efficiency ratio

MSE = Mechanical Specific Energy (psi)

Power Graph

bull Actual Data

r h

t

f P

O R

Desired region Low MSE High ROP

Undesired region High MSE Low ROP

200

180

160

140

120

100

80

6040

20

0

MSE kpsi

0 100 200 300 400 500 600 700 800

100 HP 200 HP 400 HP 800 HP 1000 HP

Figure 216 Power curve for a deep water well

(23)

Note Most data points fall in the desired region of high ROP low MSE and thetransition zone This is because ROP is not usually an issue because the rocksrsquocompressive strengths are lower in deep water than onshore For this particularwell pump relief valve set point as well as ECD limited the ability to increase the flowrate to clean the hole better to promote better transfer of energy to the bit (lowerwellbore friction) With improved hole cleaning if ECD andor pump pressure donot limit flow rate the data points in the transition zone could have moved to thedesired zone on the plot Real time vibration data did not suggest any issues dueto vibration

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Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

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Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

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A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 12: Drilling Operations Look Inside

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Acknowledgement

he author would like to thank his family his

friends and colleagues in the course of his

career whose valuable advices and experiences helped

achieved the goal of writing this book

Special thanks to Sheena Reuben who helped us

with the copyediting and proof reading of this book Te author dedicates this book to those who work

together safely and efficiently to deliver energy to the

world

8162019 Drilling Operations Look Inside

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Preface

O

ften drilling programs have documented

risks and mitigations against the identified

risks Although preventative actions against the iden-

tified risks may be expressed within the program the

emphasis is usually on the mitigation barriers against

the risks Hence it is not uncommon to see the termldquorisks and mitigationsrdquo in a drilling program Tis book

was born out of the desire to deliver the same risk man-

agement concept applied in chemical plants and refin-

eries into drilling planning and operations Barriers to

risk events should include preventative barriers and

mitigation barriers Mitigation barriers are reactive the

safety and cost of wells operations can be improved bycreating preventative barriers to reduce the chance of

the risk event occurring Mitigation barriers improve

the recovery time if a risk event should occur

8162019 Drilling Operations Look Inside

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Preface xi

Tis book focuses on improving drilling operations by managing bar-

riers (both preventative and mitigation) to risk events In Chapter 1 thebasic principles of risk management are described Te chapter talks about

everything from identification of risks to creating barriers (people process

procedures and equipment) for identified risks as well as steps to help

barrier creation Chapter 2 describes the process of drilling optimization

reviewing non-productive events from offset wells or other drilling cam-

paigns categorizing non-productive time events into those that increase

ldquodrilling timerdquo and those the extend ldquoflat timerdquo and barriers to be put inplace to optimize drilling operations Chapters 3 to 13 focus on common

non-productive time events such as loss circulation well control and so on

that lead to down-time in drilling operations and barriers to the risk events

as well as monitoringcontrol barrier (eg torque and drag) Useful drilling

calculations are highlighted in Chapter 14 Chapter 15 focuses on other

continuous improvement opportunities that are not covered in Chapters

2 through 13It is my desire that this book provides useful insight into drilling

operations improvements in the area of cost and risks It is a valuable

resource for anyone involved in well planning and operations engineers

and technicians preparing risk assessments and risk workbooks engineers

involved in writing drilling procedures engineers and managers reviewing

and approving drilling programs field engineers supervisors and superin-

tendents making decisions on the fly during drilling operations and also

students wishing to pursue careers in drilling engineering and operations

Although significant effort has been made to avoid errors they are

sometimes inevitable Suggestions towards the improvement of this book

are welcome

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CHAPTER

Risk ManagementBow-ties and theldquoPPErdquo Concept

E

very activity or operation in well construc-

tion has its own associated risk(s) Te cost of

running the operation will most certainly be impacted

by the level of risk that can be taken for that partic-

ular operation ypically the running of an operation

costs less if the level of risk associated with it is highand it is higher if the level of risk is lower However

any safety incidents arising out of high-risk opera-

tions could potentially lead to catastrophic damage

which in-turn may raise the overall cost of running

the operation immensely Terefore it is important

to identify all risks associated with any operation

during well construction and to determine what levelof risk is acceptable and to what extent Risk man-

agement is the economics of finding a suitable bal-

ance between running an operation by rejecting and

1

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 10

Table 11 Comparison of preventative and mitigation barriers

Preventative Barriers Mitigation Barriers

1 Proactive Reactive

2 Reduce the likelihood of an eventoccurring

Reduce the impact of an event

3 Involve elimination preventionand control

Involve mitigation and a recovery plan

4 Usually engineering design (welltrajectory design BHA designmud design) administrativeactions (eg enforcement ofbuffer zones) andor procedural(eg ensuring pipe movement toprevent differentially stuck pipe)

Personal and environmental protectionpersonal protective equipment (PPE)and Contingency plansproceduresCan also be engineering actions (egconstruction of berms for spill contain-ment) or administrative actions (egrestricting access to only essentialpersonnel during a well control event)

Figure 13 Bow-tie for stuck pipe

Causes

High Side ForceWelbore

Trajectory

Fluid LossAdditives

ReduceOverbalance

Jars in BottomHole Assembly

(BHA)

Stuck PipeContingency Plan

Sidetrack Plan

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Stuck PipeContingency Plan

Sidetrack Plan

Stuck PipeContingency Plan

Sidetrack Plan

Jars in BHA

Jars in BHA

StuckPipe

Hazard(Drilling)

Pull Pipe intoCasing when not

Rotating and

Circulating

Stabilizers inBHADrill Pipe

Protectors onon Drill Pipe

Control DoglegSeverity

FluidsPropertiesTracking

Contact Area

ExcessiveOverbalance

Event

ConsequenceMitigation BarriersPreventative Barriers

Use SpiralDrill Collars

in Bottom HoleAssembly (BHA)

adding fluid loss additive and filter cake reduction and using spiral

drill collars stabilizers and drill pipe protectors to minimize contact

areaControl Stuck pipe event can be controlled by creating a procedure that

ensures pipe movement during repairs for surface and downhole failures

when possible and also tracking fluid properties

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Drilling Operations Cost and Risk Management 16

Drilling optimization can be broken down into the following

bull Drilling time improvement Drilling time inefficiencies are factors

that affect the rate of penetration Examples are

use of the wrong drill bit for formation drilled

poor mud motorrotary steerable system tool selection

limitation of solid handling equipment

drill string vibrationbuckling

pump limitation for hole cleaning

drill string size causing high pump pressure unavailability or inadequate procedures for hole cleaning

data transfer limitation

bull Flat time reduction Flat time inefficiencies could be as a result of

events that change drilling time to flat time or events that extend flat

time Examples of events that change drilling time to flat time are

lost circulation

motor failure MWD (measurement while drilling) failure

bit failure

drill string failure

stuck pipe

well control

wellbore instability

failure of surface and downhole equipment casing wear

Examples of events that extend flat time are

suboptimal wellbore trajectoryhole tortuosity for casing run-

ning and logging ndash longer casing runninglogging time

swabsurge during casing running

excessive breaking circulationmud conditioning

inefficiency breaking circulation while running casingpipe

leading to losses

wellbore instability while drilling loggingrunning casing

excessive time to pull out of hole with drill string due to swab

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Drilling Operations Cost and Risk Management 22

review offset risks and the result of the offset analysis should be incorporated

into the new well design Te drilling engineerteam need to involve the

stakeholders right from the beginning of the planning process Drillingengineers should involve technical specialists other teamspeers as needed

Tey should involve vendors and suppliers too in order to utilize their

specialized knowledge new technology and database of offset wells since

Figure 27 Drilling optimization process flow

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Drilling Optimization 35

Power HP E WOB ROP

N T

m

b

( ) = times times times times( )

+ times times( ) + times

minus5 054 10

377 14 6 765 10

7

minusminus times times times times

3 2 2

4

ρ Q D ROP

d e

Where

E m = Mechanical efficiency ratio

MSE = Mechanical Specific Energy (psi)

Power Graph

bull Actual Data

r h

t

f P

O R

Desired region Low MSE High ROP

Undesired region High MSE Low ROP

200

180

160

140

120

100

80

6040

20

0

MSE kpsi

0 100 200 300 400 500 600 700 800

100 HP 200 HP 400 HP 800 HP 1000 HP

Figure 216 Power curve for a deep water well

(23)

Note Most data points fall in the desired region of high ROP low MSE and thetransition zone This is because ROP is not usually an issue because the rocksrsquocompressive strengths are lower in deep water than onshore For this particularwell pump relief valve set point as well as ECD limited the ability to increase the flowrate to clean the hole better to promote better transfer of energy to the bit (lowerwellbore friction) With improved hole cleaning if ECD andor pump pressure donot limit flow rate the data points in the transition zone could have moved to thedesired zone on the plot Real time vibration data did not suggest any issues dueto vibration

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Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

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Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

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A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 13: Drilling Operations Look Inside

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Preface

O

ften drilling programs have documented

risks and mitigations against the identified

risks Although preventative actions against the iden-

tified risks may be expressed within the program the

emphasis is usually on the mitigation barriers against

the risks Hence it is not uncommon to see the termldquorisks and mitigationsrdquo in a drilling program Tis book

was born out of the desire to deliver the same risk man-

agement concept applied in chemical plants and refin-

eries into drilling planning and operations Barriers to

risk events should include preventative barriers and

mitigation barriers Mitigation barriers are reactive the

safety and cost of wells operations can be improved bycreating preventative barriers to reduce the chance of

the risk event occurring Mitigation barriers improve

the recovery time if a risk event should occur

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Preface xi

Tis book focuses on improving drilling operations by managing bar-

riers (both preventative and mitigation) to risk events In Chapter 1 thebasic principles of risk management are described Te chapter talks about

everything from identification of risks to creating barriers (people process

procedures and equipment) for identified risks as well as steps to help

barrier creation Chapter 2 describes the process of drilling optimization

reviewing non-productive events from offset wells or other drilling cam-

paigns categorizing non-productive time events into those that increase

ldquodrilling timerdquo and those the extend ldquoflat timerdquo and barriers to be put inplace to optimize drilling operations Chapters 3 to 13 focus on common

non-productive time events such as loss circulation well control and so on

that lead to down-time in drilling operations and barriers to the risk events

as well as monitoringcontrol barrier (eg torque and drag) Useful drilling

calculations are highlighted in Chapter 14 Chapter 15 focuses on other

continuous improvement opportunities that are not covered in Chapters

2 through 13It is my desire that this book provides useful insight into drilling

operations improvements in the area of cost and risks It is a valuable

resource for anyone involved in well planning and operations engineers

and technicians preparing risk assessments and risk workbooks engineers

involved in writing drilling procedures engineers and managers reviewing

and approving drilling programs field engineers supervisors and superin-

tendents making decisions on the fly during drilling operations and also

students wishing to pursue careers in drilling engineering and operations

Although significant effort has been made to avoid errors they are

sometimes inevitable Suggestions towards the improvement of this book

are welcome

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CHAPTER

Risk ManagementBow-ties and theldquoPPErdquo Concept

E

very activity or operation in well construc-

tion has its own associated risk(s) Te cost of

running the operation will most certainly be impacted

by the level of risk that can be taken for that partic-

ular operation ypically the running of an operation

costs less if the level of risk associated with it is highand it is higher if the level of risk is lower However

any safety incidents arising out of high-risk opera-

tions could potentially lead to catastrophic damage

which in-turn may raise the overall cost of running

the operation immensely Terefore it is important

to identify all risks associated with any operation

during well construction and to determine what levelof risk is acceptable and to what extent Risk man-

agement is the economics of finding a suitable bal-

ance between running an operation by rejecting and

1

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Drilling Operations Cost and Risk Management 10

Table 11 Comparison of preventative and mitigation barriers

Preventative Barriers Mitigation Barriers

1 Proactive Reactive

2 Reduce the likelihood of an eventoccurring

Reduce the impact of an event

3 Involve elimination preventionand control

Involve mitigation and a recovery plan

4 Usually engineering design (welltrajectory design BHA designmud design) administrativeactions (eg enforcement ofbuffer zones) andor procedural(eg ensuring pipe movement toprevent differentially stuck pipe)

Personal and environmental protectionpersonal protective equipment (PPE)and Contingency plansproceduresCan also be engineering actions (egconstruction of berms for spill contain-ment) or administrative actions (egrestricting access to only essentialpersonnel during a well control event)

Figure 13 Bow-tie for stuck pipe

Causes

High Side ForceWelbore

Trajectory

Fluid LossAdditives

ReduceOverbalance

Jars in BottomHole Assembly

(BHA)

Stuck PipeContingency Plan

Sidetrack Plan

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Stuck PipeContingency Plan

Sidetrack Plan

Stuck PipeContingency Plan

Sidetrack Plan

Jars in BHA

Jars in BHA

StuckPipe

Hazard(Drilling)

Pull Pipe intoCasing when not

Rotating and

Circulating

Stabilizers inBHADrill Pipe

Protectors onon Drill Pipe

Control DoglegSeverity

FluidsPropertiesTracking

Contact Area

ExcessiveOverbalance

Event

ConsequenceMitigation BarriersPreventative Barriers

Use SpiralDrill Collars

in Bottom HoleAssembly (BHA)

adding fluid loss additive and filter cake reduction and using spiral

drill collars stabilizers and drill pipe protectors to minimize contact

areaControl Stuck pipe event can be controlled by creating a procedure that

ensures pipe movement during repairs for surface and downhole failures

when possible and also tracking fluid properties

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Drilling Operations Cost and Risk Management 16

Drilling optimization can be broken down into the following

bull Drilling time improvement Drilling time inefficiencies are factors

that affect the rate of penetration Examples are

use of the wrong drill bit for formation drilled

poor mud motorrotary steerable system tool selection

limitation of solid handling equipment

drill string vibrationbuckling

pump limitation for hole cleaning

drill string size causing high pump pressure unavailability or inadequate procedures for hole cleaning

data transfer limitation

bull Flat time reduction Flat time inefficiencies could be as a result of

events that change drilling time to flat time or events that extend flat

time Examples of events that change drilling time to flat time are

lost circulation

motor failure MWD (measurement while drilling) failure

bit failure

drill string failure

stuck pipe

well control

wellbore instability

failure of surface and downhole equipment casing wear

Examples of events that extend flat time are

suboptimal wellbore trajectoryhole tortuosity for casing run-

ning and logging ndash longer casing runninglogging time

swabsurge during casing running

excessive breaking circulationmud conditioning

inefficiency breaking circulation while running casingpipe

leading to losses

wellbore instability while drilling loggingrunning casing

excessive time to pull out of hole with drill string due to swab

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Drilling Operations Cost and Risk Management 22

review offset risks and the result of the offset analysis should be incorporated

into the new well design Te drilling engineerteam need to involve the

stakeholders right from the beginning of the planning process Drillingengineers should involve technical specialists other teamspeers as needed

Tey should involve vendors and suppliers too in order to utilize their

specialized knowledge new technology and database of offset wells since

Figure 27 Drilling optimization process flow

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Drilling Optimization 35

Power HP E WOB ROP

N T

m

b

( ) = times times times times( )

+ times times( ) + times

minus5 054 10

377 14 6 765 10

7

minusminus times times times times

3 2 2

4

ρ Q D ROP

d e

Where

E m = Mechanical efficiency ratio

MSE = Mechanical Specific Energy (psi)

Power Graph

bull Actual Data

r h

t

f P

O R

Desired region Low MSE High ROP

Undesired region High MSE Low ROP

200

180

160

140

120

100

80

6040

20

0

MSE kpsi

0 100 200 300 400 500 600 700 800

100 HP 200 HP 400 HP 800 HP 1000 HP

Figure 216 Power curve for a deep water well

(23)

Note Most data points fall in the desired region of high ROP low MSE and thetransition zone This is because ROP is not usually an issue because the rocksrsquocompressive strengths are lower in deep water than onshore For this particularwell pump relief valve set point as well as ECD limited the ability to increase the flowrate to clean the hole better to promote better transfer of energy to the bit (lowerwellbore friction) With improved hole cleaning if ECD andor pump pressure donot limit flow rate the data points in the transition zone could have moved to thedesired zone on the plot Real time vibration data did not suggest any issues dueto vibration

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Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

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Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

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A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 14: Drilling Operations Look Inside

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Preface xi

Tis book focuses on improving drilling operations by managing bar-

riers (both preventative and mitigation) to risk events In Chapter 1 thebasic principles of risk management are described Te chapter talks about

everything from identification of risks to creating barriers (people process

procedures and equipment) for identified risks as well as steps to help

barrier creation Chapter 2 describes the process of drilling optimization

reviewing non-productive events from offset wells or other drilling cam-

paigns categorizing non-productive time events into those that increase

ldquodrilling timerdquo and those the extend ldquoflat timerdquo and barriers to be put inplace to optimize drilling operations Chapters 3 to 13 focus on common

non-productive time events such as loss circulation well control and so on

that lead to down-time in drilling operations and barriers to the risk events

as well as monitoringcontrol barrier (eg torque and drag) Useful drilling

calculations are highlighted in Chapter 14 Chapter 15 focuses on other

continuous improvement opportunities that are not covered in Chapters

2 through 13It is my desire that this book provides useful insight into drilling

operations improvements in the area of cost and risks It is a valuable

resource for anyone involved in well planning and operations engineers

and technicians preparing risk assessments and risk workbooks engineers

involved in writing drilling procedures engineers and managers reviewing

and approving drilling programs field engineers supervisors and superin-

tendents making decisions on the fly during drilling operations and also

students wishing to pursue careers in drilling engineering and operations

Although significant effort has been made to avoid errors they are

sometimes inevitable Suggestions towards the improvement of this book

are welcome

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CHAPTER

Risk ManagementBow-ties and theldquoPPErdquo Concept

E

very activity or operation in well construc-

tion has its own associated risk(s) Te cost of

running the operation will most certainly be impacted

by the level of risk that can be taken for that partic-

ular operation ypically the running of an operation

costs less if the level of risk associated with it is highand it is higher if the level of risk is lower However

any safety incidents arising out of high-risk opera-

tions could potentially lead to catastrophic damage

which in-turn may raise the overall cost of running

the operation immensely Terefore it is important

to identify all risks associated with any operation

during well construction and to determine what levelof risk is acceptable and to what extent Risk man-

agement is the economics of finding a suitable bal-

ance between running an operation by rejecting and

1

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Drilling Operations Cost and Risk Management 10

Table 11 Comparison of preventative and mitigation barriers

Preventative Barriers Mitigation Barriers

1 Proactive Reactive

2 Reduce the likelihood of an eventoccurring

Reduce the impact of an event

3 Involve elimination preventionand control

Involve mitigation and a recovery plan

4 Usually engineering design (welltrajectory design BHA designmud design) administrativeactions (eg enforcement ofbuffer zones) andor procedural(eg ensuring pipe movement toprevent differentially stuck pipe)

Personal and environmental protectionpersonal protective equipment (PPE)and Contingency plansproceduresCan also be engineering actions (egconstruction of berms for spill contain-ment) or administrative actions (egrestricting access to only essentialpersonnel during a well control event)

Figure 13 Bow-tie for stuck pipe

Causes

High Side ForceWelbore

Trajectory

Fluid LossAdditives

ReduceOverbalance

Jars in BottomHole Assembly

(BHA)

Stuck PipeContingency Plan

Sidetrack Plan

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Stuck PipeContingency Plan

Sidetrack Plan

Stuck PipeContingency Plan

Sidetrack Plan

Jars in BHA

Jars in BHA

StuckPipe

Hazard(Drilling)

Pull Pipe intoCasing when not

Rotating and

Circulating

Stabilizers inBHADrill Pipe

Protectors onon Drill Pipe

Control DoglegSeverity

FluidsPropertiesTracking

Contact Area

ExcessiveOverbalance

Event

ConsequenceMitigation BarriersPreventative Barriers

Use SpiralDrill Collars

in Bottom HoleAssembly (BHA)

adding fluid loss additive and filter cake reduction and using spiral

drill collars stabilizers and drill pipe protectors to minimize contact

areaControl Stuck pipe event can be controlled by creating a procedure that

ensures pipe movement during repairs for surface and downhole failures

when possible and also tracking fluid properties

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Drilling Operations Cost and Risk Management 16

Drilling optimization can be broken down into the following

bull Drilling time improvement Drilling time inefficiencies are factors

that affect the rate of penetration Examples are

use of the wrong drill bit for formation drilled

poor mud motorrotary steerable system tool selection

limitation of solid handling equipment

drill string vibrationbuckling

pump limitation for hole cleaning

drill string size causing high pump pressure unavailability or inadequate procedures for hole cleaning

data transfer limitation

bull Flat time reduction Flat time inefficiencies could be as a result of

events that change drilling time to flat time or events that extend flat

time Examples of events that change drilling time to flat time are

lost circulation

motor failure MWD (measurement while drilling) failure

bit failure

drill string failure

stuck pipe

well control

wellbore instability

failure of surface and downhole equipment casing wear

Examples of events that extend flat time are

suboptimal wellbore trajectoryhole tortuosity for casing run-

ning and logging ndash longer casing runninglogging time

swabsurge during casing running

excessive breaking circulationmud conditioning

inefficiency breaking circulation while running casingpipe

leading to losses

wellbore instability while drilling loggingrunning casing

excessive time to pull out of hole with drill string due to swab

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 22

review offset risks and the result of the offset analysis should be incorporated

into the new well design Te drilling engineerteam need to involve the

stakeholders right from the beginning of the planning process Drillingengineers should involve technical specialists other teamspeers as needed

Tey should involve vendors and suppliers too in order to utilize their

specialized knowledge new technology and database of offset wells since

Figure 27 Drilling optimization process flow

8162019 Drilling Operations Look Inside

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Drilling Optimization 35

Power HP E WOB ROP

N T

m

b

( ) = times times times times( )

+ times times( ) + times

minus5 054 10

377 14 6 765 10

7

minusminus times times times times

3 2 2

4

ρ Q D ROP

d e

Where

E m = Mechanical efficiency ratio

MSE = Mechanical Specific Energy (psi)

Power Graph

bull Actual Data

r h

t

f P

O R

Desired region Low MSE High ROP

Undesired region High MSE Low ROP

200

180

160

140

120

100

80

6040

20

0

MSE kpsi

0 100 200 300 400 500 600 700 800

100 HP 200 HP 400 HP 800 HP 1000 HP

Figure 216 Power curve for a deep water well

(23)

Note Most data points fall in the desired region of high ROP low MSE and thetransition zone This is because ROP is not usually an issue because the rocksrsquocompressive strengths are lower in deep water than onshore For this particularwell pump relief valve set point as well as ECD limited the ability to increase the flowrate to clean the hole better to promote better transfer of energy to the bit (lowerwellbore friction) With improved hole cleaning if ECD andor pump pressure donot limit flow rate the data points in the transition zone could have moved to thedesired zone on the plot Real time vibration data did not suggest any issues dueto vibration

8162019 Drilling Operations Look Inside

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Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

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Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

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8162019 Drilling Operations Look Inside

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A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 15: Drilling Operations Look Inside

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CHAPTER

Risk ManagementBow-ties and theldquoPPErdquo Concept

E

very activity or operation in well construc-

tion has its own associated risk(s) Te cost of

running the operation will most certainly be impacted

by the level of risk that can be taken for that partic-

ular operation ypically the running of an operation

costs less if the level of risk associated with it is highand it is higher if the level of risk is lower However

any safety incidents arising out of high-risk opera-

tions could potentially lead to catastrophic damage

which in-turn may raise the overall cost of running

the operation immensely Terefore it is important

to identify all risks associated with any operation

during well construction and to determine what levelof risk is acceptable and to what extent Risk man-

agement is the economics of finding a suitable bal-

ance between running an operation by rejecting and

1

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Drilling Operations Cost and Risk Management 10

Table 11 Comparison of preventative and mitigation barriers

Preventative Barriers Mitigation Barriers

1 Proactive Reactive

2 Reduce the likelihood of an eventoccurring

Reduce the impact of an event

3 Involve elimination preventionand control

Involve mitigation and a recovery plan

4 Usually engineering design (welltrajectory design BHA designmud design) administrativeactions (eg enforcement ofbuffer zones) andor procedural(eg ensuring pipe movement toprevent differentially stuck pipe)

Personal and environmental protectionpersonal protective equipment (PPE)and Contingency plansproceduresCan also be engineering actions (egconstruction of berms for spill contain-ment) or administrative actions (egrestricting access to only essentialpersonnel during a well control event)

Figure 13 Bow-tie for stuck pipe

Causes

High Side ForceWelbore

Trajectory

Fluid LossAdditives

ReduceOverbalance

Jars in BottomHole Assembly

(BHA)

Stuck PipeContingency Plan

Sidetrack Plan

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Stuck PipeContingency Plan

Sidetrack Plan

Stuck PipeContingency Plan

Sidetrack Plan

Jars in BHA

Jars in BHA

StuckPipe

Hazard(Drilling)

Pull Pipe intoCasing when not

Rotating and

Circulating

Stabilizers inBHADrill Pipe

Protectors onon Drill Pipe

Control DoglegSeverity

FluidsPropertiesTracking

Contact Area

ExcessiveOverbalance

Event

ConsequenceMitigation BarriersPreventative Barriers

Use SpiralDrill Collars

in Bottom HoleAssembly (BHA)

adding fluid loss additive and filter cake reduction and using spiral

drill collars stabilizers and drill pipe protectors to minimize contact

areaControl Stuck pipe event can be controlled by creating a procedure that

ensures pipe movement during repairs for surface and downhole failures

when possible and also tracking fluid properties

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Drilling Operations Cost and Risk Management 16

Drilling optimization can be broken down into the following

bull Drilling time improvement Drilling time inefficiencies are factors

that affect the rate of penetration Examples are

use of the wrong drill bit for formation drilled

poor mud motorrotary steerable system tool selection

limitation of solid handling equipment

drill string vibrationbuckling

pump limitation for hole cleaning

drill string size causing high pump pressure unavailability or inadequate procedures for hole cleaning

data transfer limitation

bull Flat time reduction Flat time inefficiencies could be as a result of

events that change drilling time to flat time or events that extend flat

time Examples of events that change drilling time to flat time are

lost circulation

motor failure MWD (measurement while drilling) failure

bit failure

drill string failure

stuck pipe

well control

wellbore instability

failure of surface and downhole equipment casing wear

Examples of events that extend flat time are

suboptimal wellbore trajectoryhole tortuosity for casing run-

ning and logging ndash longer casing runninglogging time

swabsurge during casing running

excessive breaking circulationmud conditioning

inefficiency breaking circulation while running casingpipe

leading to losses

wellbore instability while drilling loggingrunning casing

excessive time to pull out of hole with drill string due to swab

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Drilling Operations Cost and Risk Management 22

review offset risks and the result of the offset analysis should be incorporated

into the new well design Te drilling engineerteam need to involve the

stakeholders right from the beginning of the planning process Drillingengineers should involve technical specialists other teamspeers as needed

Tey should involve vendors and suppliers too in order to utilize their

specialized knowledge new technology and database of offset wells since

Figure 27 Drilling optimization process flow

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Drilling Optimization 35

Power HP E WOB ROP

N T

m

b

( ) = times times times times( )

+ times times( ) + times

minus5 054 10

377 14 6 765 10

7

minusminus times times times times

3 2 2

4

ρ Q D ROP

d e

Where

E m = Mechanical efficiency ratio

MSE = Mechanical Specific Energy (psi)

Power Graph

bull Actual Data

r h

t

f P

O R

Desired region Low MSE High ROP

Undesired region High MSE Low ROP

200

180

160

140

120

100

80

6040

20

0

MSE kpsi

0 100 200 300 400 500 600 700 800

100 HP 200 HP 400 HP 800 HP 1000 HP

Figure 216 Power curve for a deep water well

(23)

Note Most data points fall in the desired region of high ROP low MSE and thetransition zone This is because ROP is not usually an issue because the rocksrsquocompressive strengths are lower in deep water than onshore For this particularwell pump relief valve set point as well as ECD limited the ability to increase the flowrate to clean the hole better to promote better transfer of energy to the bit (lowerwellbore friction) With improved hole cleaning if ECD andor pump pressure donot limit flow rate the data points in the transition zone could have moved to thedesired zone on the plot Real time vibration data did not suggest any issues dueto vibration

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Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

8162019 Drilling Operations Look Inside

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

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Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

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8162019 Drilling Operations Look Inside

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A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 16: Drilling Operations Look Inside

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CHAPTER

Risk ManagementBow-ties and theldquoPPErdquo Concept

E

very activity or operation in well construc-

tion has its own associated risk(s) Te cost of

running the operation will most certainly be impacted

by the level of risk that can be taken for that partic-

ular operation ypically the running of an operation

costs less if the level of risk associated with it is highand it is higher if the level of risk is lower However

any safety incidents arising out of high-risk opera-

tions could potentially lead to catastrophic damage

which in-turn may raise the overall cost of running

the operation immensely Terefore it is important

to identify all risks associated with any operation

during well construction and to determine what levelof risk is acceptable and to what extent Risk man-

agement is the economics of finding a suitable bal-

ance between running an operation by rejecting and

1

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Drilling Operations Cost and Risk Management 10

Table 11 Comparison of preventative and mitigation barriers

Preventative Barriers Mitigation Barriers

1 Proactive Reactive

2 Reduce the likelihood of an eventoccurring

Reduce the impact of an event

3 Involve elimination preventionand control

Involve mitigation and a recovery plan

4 Usually engineering design (welltrajectory design BHA designmud design) administrativeactions (eg enforcement ofbuffer zones) andor procedural(eg ensuring pipe movement toprevent differentially stuck pipe)

Personal and environmental protectionpersonal protective equipment (PPE)and Contingency plansproceduresCan also be engineering actions (egconstruction of berms for spill contain-ment) or administrative actions (egrestricting access to only essentialpersonnel during a well control event)

Figure 13 Bow-tie for stuck pipe

Causes

High Side ForceWelbore

Trajectory

Fluid LossAdditives

ReduceOverbalance

Jars in BottomHole Assembly

(BHA)

Stuck PipeContingency Plan

Sidetrack Plan

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Stuck PipeContingency Plan

Sidetrack Plan

Stuck PipeContingency Plan

Sidetrack Plan

Jars in BHA

Jars in BHA

StuckPipe

Hazard(Drilling)

Pull Pipe intoCasing when not

Rotating and

Circulating

Stabilizers inBHADrill Pipe

Protectors onon Drill Pipe

Control DoglegSeverity

FluidsPropertiesTracking

Contact Area

ExcessiveOverbalance

Event

ConsequenceMitigation BarriersPreventative Barriers

Use SpiralDrill Collars

in Bottom HoleAssembly (BHA)

adding fluid loss additive and filter cake reduction and using spiral

drill collars stabilizers and drill pipe protectors to minimize contact

areaControl Stuck pipe event can be controlled by creating a procedure that

ensures pipe movement during repairs for surface and downhole failures

when possible and also tracking fluid properties

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Drilling Operations Cost and Risk Management 16

Drilling optimization can be broken down into the following

bull Drilling time improvement Drilling time inefficiencies are factors

that affect the rate of penetration Examples are

use of the wrong drill bit for formation drilled

poor mud motorrotary steerable system tool selection

limitation of solid handling equipment

drill string vibrationbuckling

pump limitation for hole cleaning

drill string size causing high pump pressure unavailability or inadequate procedures for hole cleaning

data transfer limitation

bull Flat time reduction Flat time inefficiencies could be as a result of

events that change drilling time to flat time or events that extend flat

time Examples of events that change drilling time to flat time are

lost circulation

motor failure MWD (measurement while drilling) failure

bit failure

drill string failure

stuck pipe

well control

wellbore instability

failure of surface and downhole equipment casing wear

Examples of events that extend flat time are

suboptimal wellbore trajectoryhole tortuosity for casing run-

ning and logging ndash longer casing runninglogging time

swabsurge during casing running

excessive breaking circulationmud conditioning

inefficiency breaking circulation while running casingpipe

leading to losses

wellbore instability while drilling loggingrunning casing

excessive time to pull out of hole with drill string due to swab

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Drilling Operations Cost and Risk Management 22

review offset risks and the result of the offset analysis should be incorporated

into the new well design Te drilling engineerteam need to involve the

stakeholders right from the beginning of the planning process Drillingengineers should involve technical specialists other teamspeers as needed

Tey should involve vendors and suppliers too in order to utilize their

specialized knowledge new technology and database of offset wells since

Figure 27 Drilling optimization process flow

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Drilling Optimization 35

Power HP E WOB ROP

N T

m

b

( ) = times times times times( )

+ times times( ) + times

minus5 054 10

377 14 6 765 10

7

minusminus times times times times

3 2 2

4

ρ Q D ROP

d e

Where

E m = Mechanical efficiency ratio

MSE = Mechanical Specific Energy (psi)

Power Graph

bull Actual Data

r h

t

f P

O R

Desired region Low MSE High ROP

Undesired region High MSE Low ROP

200

180

160

140

120

100

80

6040

20

0

MSE kpsi

0 100 200 300 400 500 600 700 800

100 HP 200 HP 400 HP 800 HP 1000 HP

Figure 216 Power curve for a deep water well

(23)

Note Most data points fall in the desired region of high ROP low MSE and thetransition zone This is because ROP is not usually an issue because the rocksrsquocompressive strengths are lower in deep water than onshore For this particularwell pump relief valve set point as well as ECD limited the ability to increase the flowrate to clean the hole better to promote better transfer of energy to the bit (lowerwellbore friction) With improved hole cleaning if ECD andor pump pressure donot limit flow rate the data points in the transition zone could have moved to thedesired zone on the plot Real time vibration data did not suggest any issues dueto vibration

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Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

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Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

8162019 Drilling Operations Look Inside

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

8162019 Drilling Operations Look Inside

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

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8162019 Drilling Operations Look Inside

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A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 17: Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 10

Table 11 Comparison of preventative and mitigation barriers

Preventative Barriers Mitigation Barriers

1 Proactive Reactive

2 Reduce the likelihood of an eventoccurring

Reduce the impact of an event

3 Involve elimination preventionand control

Involve mitigation and a recovery plan

4 Usually engineering design (welltrajectory design BHA designmud design) administrativeactions (eg enforcement ofbuffer zones) andor procedural(eg ensuring pipe movement toprevent differentially stuck pipe)

Personal and environmental protectionpersonal protective equipment (PPE)and Contingency plansproceduresCan also be engineering actions (egconstruction of berms for spill contain-ment) or administrative actions (egrestricting access to only essentialpersonnel during a well control event)

Figure 13 Bow-tie for stuck pipe

Causes

High Side ForceWelbore

Trajectory

Fluid LossAdditives

ReduceOverbalance

Jars in BottomHole Assembly

(BHA)

Stuck PipeContingency Plan

Sidetrack Plan

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Increased Well Cost Well Control Event

Loss Circulation

Stuck PipeContingency Plan

Sidetrack Plan

Stuck PipeContingency Plan

Sidetrack Plan

Jars in BHA

Jars in BHA

StuckPipe

Hazard(Drilling)

Pull Pipe intoCasing when not

Rotating and

Circulating

Stabilizers inBHADrill Pipe

Protectors onon Drill Pipe

Control DoglegSeverity

FluidsPropertiesTracking

Contact Area

ExcessiveOverbalance

Event

ConsequenceMitigation BarriersPreventative Barriers

Use SpiralDrill Collars

in Bottom HoleAssembly (BHA)

adding fluid loss additive and filter cake reduction and using spiral

drill collars stabilizers and drill pipe protectors to minimize contact

areaControl Stuck pipe event can be controlled by creating a procedure that

ensures pipe movement during repairs for surface and downhole failures

when possible and also tracking fluid properties

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Drilling Operations Cost and Risk Management 16

Drilling optimization can be broken down into the following

bull Drilling time improvement Drilling time inefficiencies are factors

that affect the rate of penetration Examples are

use of the wrong drill bit for formation drilled

poor mud motorrotary steerable system tool selection

limitation of solid handling equipment

drill string vibrationbuckling

pump limitation for hole cleaning

drill string size causing high pump pressure unavailability or inadequate procedures for hole cleaning

data transfer limitation

bull Flat time reduction Flat time inefficiencies could be as a result of

events that change drilling time to flat time or events that extend flat

time Examples of events that change drilling time to flat time are

lost circulation

motor failure MWD (measurement while drilling) failure

bit failure

drill string failure

stuck pipe

well control

wellbore instability

failure of surface and downhole equipment casing wear

Examples of events that extend flat time are

suboptimal wellbore trajectoryhole tortuosity for casing run-

ning and logging ndash longer casing runninglogging time

swabsurge during casing running

excessive breaking circulationmud conditioning

inefficiency breaking circulation while running casingpipe

leading to losses

wellbore instability while drilling loggingrunning casing

excessive time to pull out of hole with drill string due to swab

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Drilling Operations Cost and Risk Management 22

review offset risks and the result of the offset analysis should be incorporated

into the new well design Te drilling engineerteam need to involve the

stakeholders right from the beginning of the planning process Drillingengineers should involve technical specialists other teamspeers as needed

Tey should involve vendors and suppliers too in order to utilize their

specialized knowledge new technology and database of offset wells since

Figure 27 Drilling optimization process flow

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Drilling Optimization 35

Power HP E WOB ROP

N T

m

b

( ) = times times times times( )

+ times times( ) + times

minus5 054 10

377 14 6 765 10

7

minusminus times times times times

3 2 2

4

ρ Q D ROP

d e

Where

E m = Mechanical efficiency ratio

MSE = Mechanical Specific Energy (psi)

Power Graph

bull Actual Data

r h

t

f P

O R

Desired region Low MSE High ROP

Undesired region High MSE Low ROP

200

180

160

140

120

100

80

6040

20

0

MSE kpsi

0 100 200 300 400 500 600 700 800

100 HP 200 HP 400 HP 800 HP 1000 HP

Figure 216 Power curve for a deep water well

(23)

Note Most data points fall in the desired region of high ROP low MSE and thetransition zone This is because ROP is not usually an issue because the rocksrsquocompressive strengths are lower in deep water than onshore For this particularwell pump relief valve set point as well as ECD limited the ability to increase the flowrate to clean the hole better to promote better transfer of energy to the bit (lowerwellbore friction) With improved hole cleaning if ECD andor pump pressure donot limit flow rate the data points in the transition zone could have moved to thedesired zone on the plot Real time vibration data did not suggest any issues dueto vibration

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Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

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Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

8162019 Drilling Operations Look Inside

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8162019 Drilling Operations Look Inside

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A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 18: Drilling Operations Look Inside

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 1833

Drilling Operations Cost and Risk Management 16

Drilling optimization can be broken down into the following

bull Drilling time improvement Drilling time inefficiencies are factors

that affect the rate of penetration Examples are

use of the wrong drill bit for formation drilled

poor mud motorrotary steerable system tool selection

limitation of solid handling equipment

drill string vibrationbuckling

pump limitation for hole cleaning

drill string size causing high pump pressure unavailability or inadequate procedures for hole cleaning

data transfer limitation

bull Flat time reduction Flat time inefficiencies could be as a result of

events that change drilling time to flat time or events that extend flat

time Examples of events that change drilling time to flat time are

lost circulation

motor failure MWD (measurement while drilling) failure

bit failure

drill string failure

stuck pipe

well control

wellbore instability

failure of surface and downhole equipment casing wear

Examples of events that extend flat time are

suboptimal wellbore trajectoryhole tortuosity for casing run-

ning and logging ndash longer casing runninglogging time

swabsurge during casing running

excessive breaking circulationmud conditioning

inefficiency breaking circulation while running casingpipe

leading to losses

wellbore instability while drilling loggingrunning casing

excessive time to pull out of hole with drill string due to swab

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 22

review offset risks and the result of the offset analysis should be incorporated

into the new well design Te drilling engineerteam need to involve the

stakeholders right from the beginning of the planning process Drillingengineers should involve technical specialists other teamspeers as needed

Tey should involve vendors and suppliers too in order to utilize their

specialized knowledge new technology and database of offset wells since

Figure 27 Drilling optimization process flow

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2033

Drilling Optimization 35

Power HP E WOB ROP

N T

m

b

( ) = times times times times( )

+ times times( ) + times

minus5 054 10

377 14 6 765 10

7

minusminus times times times times

3 2 2

4

ρ Q D ROP

d e

Where

E m = Mechanical efficiency ratio

MSE = Mechanical Specific Energy (psi)

Power Graph

bull Actual Data

r h

t

f P

O R

Desired region Low MSE High ROP

Undesired region High MSE Low ROP

200

180

160

140

120

100

80

6040

20

0

MSE kpsi

0 100 200 300 400 500 600 700 800

100 HP 200 HP 400 HP 800 HP 1000 HP

Figure 216 Power curve for a deep water well

(23)

Note Most data points fall in the desired region of high ROP low MSE and thetransition zone This is because ROP is not usually an issue because the rocksrsquocompressive strengths are lower in deep water than onshore For this particularwell pump relief valve set point as well as ECD limited the ability to increase the flowrate to clean the hole better to promote better transfer of energy to the bit (lowerwellbore friction) With improved hole cleaning if ECD andor pump pressure donot limit flow rate the data points in the transition zone could have moved to thedesired zone on the plot Real time vibration data did not suggest any issues dueto vibration

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2133

Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

8162019 Drilling Operations Look Inside

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

8162019 Drilling Operations Look Inside

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

8162019 Drilling Operations Look Inside

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3233

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3333

A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 19: Drilling Operations Look Inside

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 22

review offset risks and the result of the offset analysis should be incorporated

into the new well design Te drilling engineerteam need to involve the

stakeholders right from the beginning of the planning process Drillingengineers should involve technical specialists other teamspeers as needed

Tey should involve vendors and suppliers too in order to utilize their

specialized knowledge new technology and database of offset wells since

Figure 27 Drilling optimization process flow

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2033

Drilling Optimization 35

Power HP E WOB ROP

N T

m

b

( ) = times times times times( )

+ times times( ) + times

minus5 054 10

377 14 6 765 10

7

minusminus times times times times

3 2 2

4

ρ Q D ROP

d e

Where

E m = Mechanical efficiency ratio

MSE = Mechanical Specific Energy (psi)

Power Graph

bull Actual Data

r h

t

f P

O R

Desired region Low MSE High ROP

Undesired region High MSE Low ROP

200

180

160

140

120

100

80

6040

20

0

MSE kpsi

0 100 200 300 400 500 600 700 800

100 HP 200 HP 400 HP 800 HP 1000 HP

Figure 216 Power curve for a deep water well

(23)

Note Most data points fall in the desired region of high ROP low MSE and thetransition zone This is because ROP is not usually an issue because the rocksrsquocompressive strengths are lower in deep water than onshore For this particularwell pump relief valve set point as well as ECD limited the ability to increase the flowrate to clean the hole better to promote better transfer of energy to the bit (lowerwellbore friction) With improved hole cleaning if ECD andor pump pressure donot limit flow rate the data points in the transition zone could have moved to thedesired zone on the plot Real time vibration data did not suggest any issues dueto vibration

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2133

Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

8162019 Drilling Operations Look Inside

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

8162019 Drilling Operations Look Inside

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

8162019 Drilling Operations Look Inside

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

8162019 Drilling Operations Look Inside

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8162019 Drilling Operations Look Inside

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A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 20: Drilling Operations Look Inside

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Drilling Optimization 35

Power HP E WOB ROP

N T

m

b

( ) = times times times times( )

+ times times( ) + times

minus5 054 10

377 14 6 765 10

7

minusminus times times times times

3 2 2

4

ρ Q D ROP

d e

Where

E m = Mechanical efficiency ratio

MSE = Mechanical Specific Energy (psi)

Power Graph

bull Actual Data

r h

t

f P

O R

Desired region Low MSE High ROP

Undesired region High MSE Low ROP

200

180

160

140

120

100

80

6040

20

0

MSE kpsi

0 100 200 300 400 500 600 700 800

100 HP 200 HP 400 HP 800 HP 1000 HP

Figure 216 Power curve for a deep water well

(23)

Note Most data points fall in the desired region of high ROP low MSE and thetransition zone This is because ROP is not usually an issue because the rocksrsquocompressive strengths are lower in deep water than onshore For this particularwell pump relief valve set point as well as ECD limited the ability to increase the flowrate to clean the hole better to promote better transfer of energy to the bit (lowerwellbore friction) With improved hole cleaning if ECD andor pump pressure donot limit flow rate the data points in the transition zone could have moved to thedesired zone on the plot Real time vibration data did not suggest any issues dueto vibration

8162019 Drilling Operations Look Inside

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Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

8162019 Drilling Operations Look Inside

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2633

Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

8162019 Drilling Operations Look Inside

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

8162019 Drilling Operations Look Inside

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

8162019 Drilling Operations Look Inside

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8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3333

A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 21: Drilling Operations Look Inside

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2133

Vibration 43

shear force In this particular example an MWD was placed at about 60 ft

from the bit and it failed due to excessive vibration Tis analysis was car-

ried out after the failure but could have been really helpful and also saved

a day of non-productive time if the analysis was done prior to designing

the drill string as it would have helped with positioning the MWD away

from the high stress zone

In a major drilling program it is recommended that vibration study

should be undertaken in earlier wells to help determine ways to optimize

ROP in subsequent wells Downhole vibration tools should be run to

understand the impact of drilling parameters and formation tendencies on

vibration Figure 34 is a typical output from a vibration recording down-

hole tool When not financially constrained it is good to test as many

concepts as possible in earlier wells in order to capture as much learning as

possible and then incorporate that into subsequent well plans

Vibration could be axial lateral or torsional See Figure 35 Axial vibra-tion is the vibration along the longitudinal direction up and down the drill

string Lateral vibration occurs perpendicular to the length of the drill string

Axial and lateral vibrations occur because of insufficient downward force

0500

1000

1500

2000

2500

3000

3500

S h e a r

f o r c e

( l b f )

Distance from Bit (ft)

Vertical Transverse

0 50 100 150 200 250 300 350 400 450 500 550 600

Figure 33 Shear force on drill string from critical speed analysis

8162019 Drilling Operations Look Inside

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Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2333

Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2533

Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

8162019 Drilling Operations Look Inside

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

8162019 Drilling Operations Look Inside

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3233

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3333

A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 22: Drilling Operations Look Inside

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2233

Vibration 53

F i g u r e

3 1 1

A n e x a m p l e b o w - t i e f o r d r i l l s t r i n g v i b r a t i o n

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2433

Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2533

Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2633

Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

8162019 Drilling Operations Look Inside

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Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2833

Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

8162019 Drilling Operations Look Inside

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3033

Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

8162019 Drilling Operations Look Inside

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8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3333

A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 23: Drilling Operations Look Inside

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2333

Drilling Operations Cost and Risk Management 70

on the wellbore profile critical RPM models may predict low drill string

stress in RPM beyond the critical RPM range In this case the availableRPM for hole cleaning is higher than the critical RPM

Field experiments and laboratory studies suggest step increase in

hole cleaning performance in high-angle wells at some RPM values See

Figures 43 and 44

CUTTINGS CARRYING INDEX (CCI)

Cuttings carrying index provides a good idea on how good hole cleaning is

A CCI above 10 indicates good hole cleaning and a CCI below 05 is an indi-

cation of poor hole cleaning See the following equations for CCI estimation

CCI K AV MW

=times times

times + ( )( )400 000 1 sin θ

where

K = Low shear rate viscosityPower law constant

0

01

02

03

04

05

06

07

08

09

200

Pipe RPM

R e l a t i v e

c u t t i n g s

r e t u r n

H o l e

C l e a n i n g

E f fi c i e n c y

0 20 40 60 80 100 120 140 150 160 180

Figure 43 Cuttings returnhole cleaning variation with RPM Larger step

changes in cutting return volume occur at 100ndash120 RPM and at 150ndash180 RPM

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2633

Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2733

Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2833

Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

8162019 Drilling Operations Look Inside

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Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3133

Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

8162019 Drilling Operations Look Inside

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8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3333

A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 24: Drilling Operations Look Inside

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2433

Drilling Operations Cost and Risk Management 90

time inefficient hole cleaning high torque and drag pack-off lost circu-

lation stuck pipe and potential loss of wellbore are examples of factorsthat result in non-productive time caused by a compromise in wellbore

stability Wellbore instability can result in reduction or enlargement of the

wellbore Hole reduction limits the size of pipe that can be run affecting

casing running operation pack-off or lost circulation due to pumping into

packed-off annulus and also high ECD while cementing casing Hole

enlargement causes inefficient hole cleaning and a bad cement job Te

root cause of wellbore instability should be identified and barriersactionsgenerated to address the risk Wellbore stability problems can be forma-

tion related drilling practices related andor drill string design related

Te most effective way to solve wellbore stability problems is to eliminate

the root cause where possible However if elimination of the root cause is

cost prohibitive it is good to use other preventative and control options

including mitigation and having a contingency plan See able 71

Table 71 Barriers for wellbore instability

Elimination bull Identify fractures weakrubble zones and faults fromseismic and modify well trajectory where possible

bull Minimize wellbore inclination especially in formationsprone to wellbore instability

bull Drill in the direction of maximum horizontal stress ifdifference between minimum and maximum horizontalstresses is large

Prevention bull If the root cause in offsets is formation or fluid relatedproactively increase the mud weight and salinity tomud weight required per wellbore stability model priorto drilling the formation Add fluid loss additives tocontrol fluid loss If losses are anticipated proactivelyadd lost circulation materials to the mud system Seethe section on lost circulation

bull Optimize trip speed to prevent swab and surge whilepulling out of hole and running in hole with casingand drill pipe increase the mud weight by trip marginprior to tripping or pumping while tripping pipe out ofhole for ECD ldquopump outrdquo

bull Use continuous circulation subs while making orbreaking connections to enable continuous circulation

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2533

Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2633

Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2733

Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2833

Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2933

Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3033

Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

8162019 Drilling Operations Look Inside

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Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3233

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3333

A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 25: Drilling Operations Look Inside

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2533

Drilling Operations Cost and Risk Management 126

Te equation for summing up an arithmetic series is given by

Sum n a n d = times + minus( ) 22 1 (86)

where

n = Number of terms in the series ndash this is same as number of footage

(pump and dump interval length-L)

a = First number in the series ndash this will be same as K

d = Common difference between two terms ndash this is also equal to K

Equation (86) can be written as

V

LK L K

LK KLPAD = + minus( ) = +

22 1

2

V LK

LPAD = + 2

1 (87)

V

L D

LPAD

h= times +

2 1029 4

1

2

(88)

V

L D LPAD

h= times

+

2

2058 81

(89a)

L L L 1 1 + cong

V

L D PAD

h=

times2 2

2058 8 (89b)

ESTIMATION OF DISCHARGE FLOW RATE DURING A WELL

CONTROL EVENT

Q bpm kh P

ln r

r

s e

w

( ) = times times ∆

times

+

minus4 917 10

6

βmicro

(810)

M kh

ln r

r s e

w

= times

times

+

minus4 917 10

6

βmicro

(811)

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2633

Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2733

Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2833

Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2933

Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3033

Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3133

Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3233

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3333

A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 26: Drilling Operations Look Inside

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2633

Drilling Operations Cost and Risk Management 166

Geometrical sticking can be prevented by proper well design that

has minimum tortuosity no excessive dogleg and proper BHA selec-tion that minimizes key seating (see Wellbore Trajectory Optimization

in Chapter 15) Offset wells and experience in the area should provide

useful information necessary to select BHA components Mitigations

Figure 124 Solid body centralizers with stop collars

Figure 125 Plot of downhole torque at stuck point vs Hook load

A combination of surface torque and hook load should be sufficient to

deliver required torque at stuck point

minus30000

minus25000

minus20000

minus15000

minus10000

minus5000

0

0 100 200 300 400 500 600 700

5000

10000

15000

20000

D o w n h o l e

T o r q u e ( f t l b )

Surface Hookload (klbs)

Surface Torque at 25000 ftlb Surface Torque at 35000 ftlb

Surface Torque at 45000 ftlb

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2733

Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2833

Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2933

Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3033

Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3133

Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3233

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3333

A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 27: Drilling Operations Look Inside

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2733

Conductor Jetting 183

2 Note the corresponding depths of the values above (L2 for S 2 and

L1

for S 1

)

3 Project a line from S 1 parallel to buoyed casing weight line to S 2

Te point at which the depth corresponds to S 2 on the projected

line is S 3

4 Estimate the average ROP between the two points (ROP in ftmin)

5 Calculate time taken from L1 to L2 (T dr ) using

T L L

ft mindr

ave

hr

ROP

( ) =minus

( )times2 1

60

6 Calculate the rate of change of slack-off value using

S

S S

T r dr

=

minus2 3

00

50

100

150

200

250

300

50000 100000 150000 200000 250000 300000

Slack-off Weight (lbs)

D e p t h B e l o w M

u d l i n e ( f t )

Jetting Slack Off Weight

Buoyed Casing Weight Buoyed Casing + Jetting BHA Weight Buckling Force

Tensile LimitActual Slack-Off WeightMaximum Set Down Weight

Max Allowable Set Down Weight

S 1

S 2

S 3

Figure 133 Determination of rate of strength development from plot of

weight on bit while jetting

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2833

Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2933

Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3033

Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3133

Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3233

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3333

A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 28: Drilling Operations Look Inside

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2833

Drilling Operations Cost and Risk Management 188

Figure 141 Mud gas separator

ChokeManifold

Pressure Gauge

Vent Line

From Flow Line

Flow Indicator

To Flow Line

Pressure Gauge(Mud Leg)

Q P d

f L

ml v

g e

gas surfaceMMSCF

day

=

times

times times times times

∆ 5

44 39 10 ρ

(143)

where

∆P ml = Pressure of mud leg (psi)

ρ mud = Density of mud (ppg)

ρ g = Density of gas (ppg)

f = Friction factor

d v = Vent line diameter (in)

hml = Height of mud leg (ft)

Le = Vent line equivalent length (ft)

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2933

Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3033

Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3133

Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3233

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3333

A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 29: Drilling Operations Look Inside

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 2933

Other Improvement Opportunities and Miscellaneous Drilling Issues 239

T a b l e 1 5 2

A n e x a m p l e h o l e s i z e s o p t i m i z a t i o

n f o r a l l t h e h o l e s e c t i o n s i n a w e l l

H o l e

S i z e

C a p a c i t y

C a s i n g

S i z e

I n i t i a l

C l e a r -

a n c e

N e w

H o l e

S i z e

N e w

C l e a r -

a n c e

N e w

C l e a r a n c e

w i t h 7 0

S t a n d - o f f

B H A

O D

( 4 0

fl o w

a r e a )

M a x i m u m

B H A O D

( 2 5 fl

o w

a r e a )

E q u i v a -

l e n t H o l e

S i z e ( E H S

)

E H S f o r

M a x i m u m

B H A

E H S

gt

C a s i n g

s i z e

E H

S

M a

x

B H A

gt

C a s i n g

s i z

e

i n

b b l f t

i n

i n

i n

i n

i n

i

n

i n

i n

i n

3 6 1

0 0

1

2 6 5 9 9

3 6

0 0

0

0 5 0

J e t t e d

3 2

5 0 0

1

0 2 6 0 8

2 8

0 0 0

2

2 5 0

3 2

0 0 0

2

0 0 0

1

4 0 0

2 4

7 9

2 7 7

1

2 9

6 0

3 0

5 7

Y e s

Y e

s

2 6

0 0 0

0

6 5 6 6 9

2 2

0 0 0

2

0 0 0

2 4

0 0 0

1

0 0 0

0 7

0 0

1 8

5 9

2 0 7

8

2 2

2 0

2 2 9

3

Y e s

Y e

s

2 2

0 0 0

0

4 7 0 1 8

1 8

0 0 0

2

0 0 0

2 0

0 0 0

1

0 0 0

0 7

0 0

1 5

4 9

1 7

3 2

1 8

5 0

1 9 1

1

Y e s

Y e

s

1 9

0 0 0

0

3 5 0 6 9

1 6

0 0 0

1

5 0 0

1 8

0 0 0

1

0 0 0

0 7

0 0

1 3

9 4

1 5

5 9

1 6

6 5

1 7

2 0

Y e s

Y e

s

1 7

0 0 0

0

2 8 0 7 5

1 4

0 0 0

1

5 0 0

1 6

0 0 0

1

0 0 0

0 7

0 0

1 2

3 9

1 3

8 6

1 4

8 0

1 5

2 9

Y e s

Y e

s

1 4

5 0 0

0

2 0 4 2 5

1 1

8 7 5

1

3 1 3

1 4

0 0 0

1

0 6 3

0 7

4 4

1 0

8 4

1 2 1

2

1 2 9

5

1 3

3 7

Y e s

Y e

s

1 2

2 5 0

0 1

4 5 7 8

9

8 7 5

1 1

8 8

1 2

0 0 0

1

0 6 3

0 7

4 4

9

3 0

1 0

3 9

1 1 1

0

1 1

4 6

Y e s

Y e

s

9

8 7 5

0

0 9 4 7 3

7 7

5 0

1

0 6 3

9

8 7 5

1

0 6 3

0 7

4 4

7

6 5

8

5 5

9 1

3

9

4 3

Y e s

Y e

s

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3033

Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3133

Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3233

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3333

A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 30: Drilling Operations Look Inside

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3033

Drilling Operations Cost and Risk Management 242

For 10000 ft of 14 casing run in singles total connection time T s

T s = minus

times =

10 000

461 0 048 10 39

hours

For 10000 ft of 14 casing run in triples total connection time t

T s = minus

times =

10 000

1401 0 048 5 16

hours

For a rig with a spread rate of 98307612 million dollar per day cost per hour is98307650000

Cost Savings = (1039 ndash 516) times 50000

= 983076261000 less cost of bucking storage and transportation

Figure 153 shows time savings as a function of number of joints per

stand and slip to slip time for the example above

Figure 153 Example time savings for 10000 ft of casing run for

different slip to slip time

1

2

3

4

5

6

000 200 400 600 800 1000 1200 1400 1600

N o

o f J o i n t s

p e r

s t a n d

Time Savings (hrs)

Time Savings for 10000 ft 14 Casing Run

3 mins slip to slip time 4 mins slip to slip time 5 mins slip to slip

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3133

Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3233

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3333

A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 31: Drilling Operations Look Inside

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3133

Drilling Operations Cost and Risk Management 262

Figure 1513 Determination of FIT pump rate from casing test and

expected FIT value

Minimum required FI value in psi can be calculated from

Minimum Required FI(psi) = 0052 times required drilling margin(ppg)

times Shoe VD (1528)

Te required drilling margin is typically 05 ppg margin above the

mud weight

INNER STRING CEMENT JOB (CONSIDER FOR LARGE OD

CASING CEMENT JOBS)

Use inner string cement job in all casing cemented prior to running

BOP (riserless section) Inner string will help avoid problems in drilling

wiper plug plug spinning and also to avoid contamination of casing ID

0

200

400

600

800

1000

1200

000 100 200 300 400 500 600 700

P r e s s u r e

p s i

Volume bbl

Casing Test FIT Expected FIT Value

Min Required FIT Value Max Volume Line Min FIT Plot Line

Min Volume Line

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3233

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3333

A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 32: Drilling Operations Look Inside

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3233

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3333

A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON

Page 33: Drilling Operations Look Inside

8162019 Drilling Operations Look Inside

httpslidepdfcomreaderfulldrilling-operations-look-inside 3333

A SigmaQuadrant EngineeringPublication

wwwSigmaquadrantcom

Positive

Displacement

Motors - Theory and Applications by Robello Samuel

Drilling Engineering

Optimization

by Robello Samuel and

JJ Azar

OTHER UPCOMING TITLE FROM

SIGMAQUADRANT

THIS BOOK is a practical guide to generate risk barriers required to manage risks and cost

during well operations Chapter 1 describes the basic principle of risk management (risk

identification risk assessment risk barrier creation and monitoring) This book covers drilling

optimization and major drilling operations non-productive time events such as hole cleaningcasing wear lost circulation wellbore stability well control and so on and providing barriers

to the risk events These barriers are sometimes presented in a table or ldquobow-tierdquo form for

clarity This book also covers useful drilling calculations during well planning and operations

as well as continuous improvement opportunities for well cost management (eg wellbore

trajectory optimization hole size optimization casing running optimization optimization of

time to break circulation wellbore monitoring during flow check after cementing and so on

Prosper Aideyan PE holds a BS in

Chemical Engineering from Louisiana

Tech University and an MEng in

Petroleum Engineering from

The University of Houston He has

over 10 years of multi-disciplinary

experience in well planning and

design well operations and process

safety with major oil and gas

companies

He is very passionate about

continuous improvement and

optimization including but not limited

to equipment design and re-design

process and procedural improvementand process parameters optimization

His book on Drilling Operations Cost

and Risk Management is based on his

experience from various successful

drilling engineering and operations

improvement projects he has worked

on during the course of his career

Prosper Aideyan is a registered

Professional Engineer in the State ofTexas USA

ABOUT THE AUTHOR

ISBN 978-0-9906836-2-9

P O S I T I V E D I S P L A C E M E N T M O T O R S - T h e or y a n d A p p l i c a t i o n s

D RI L L I N GE N GI NE E RI N G OP T I MI Z AT I ON